diff --git a/build-conventions/src/main/java/org/elasticsearch/gradle/internal/checkstyle/StringFormattingCheck.java b/build-conventions/src/main/java/org/elasticsearch/gradle/internal/checkstyle/StringFormattingCheck.java
new file mode 100644
index 0000000000000..48fa3ad6ee485
--- /dev/null
+++ b/build-conventions/src/main/java/org/elasticsearch/gradle/internal/checkstyle/StringFormattingCheck.java
@@ -0,0 +1,89 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0 and the Server Side Public License, v 1; you may not use this file except
+ * in compliance with, at your election, the Elastic License 2.0 or the Server
+ * Side Public License, v 1.
+ */
+
+package org.elasticsearch.gradle.internal.checkstyle;
+
+import com.puppycrawl.tools.checkstyle.StatelessCheck;
+import com.puppycrawl.tools.checkstyle.api.AbstractCheck;
+import com.puppycrawl.tools.checkstyle.api.DetailAST;
+import com.puppycrawl.tools.checkstyle.api.TokenTypes;
+
+import java.util.Locale;
+import java.util.regex.Matcher;
+import java.util.regex.Pattern;
+
+/**
+ * Checks for calls to {@link String#formatted(Object...)} that include format specifiers that
+ * are not locale-safe. This method always uses the default {@link Locale}, and so for our
+ * purposes it is safer to use {@link String#format(Locale, String, Object...)}.
+ * <p>
+ * Note that this rule can currently only detect violations when calling <code>formatted()</code>
+ * on a string literal or text block. In theory, it could be extended to detect violations in
+ * local variables or statics.
+ */
+@StatelessCheck
+public class StringFormattingCheck extends AbstractCheck {
+
+    public static final String FORMATTED_MSG_KEY = "forbidden.formatted";
+
+    @Override
+    public int[] getDefaultTokens() {
+        return getRequiredTokens();
+    }
+
+    @Override
+    public int[] getAcceptableTokens() {
+        return getRequiredTokens();
+    }
+
+    @Override
+    public int[] getRequiredTokens() {
+        return new int[] { TokenTypes.METHOD_CALL };
+    }
+
+    @Override
+    public void visitToken(DetailAST ast) {
+        checkFormattedMethod(ast);
+    }
+
+    // Originally pinched from java/util/Formatter.java but then modified.
+    // %[argument_index$][flags][width][.precision][t]conversion
+    private static final Pattern formatSpecifier = Pattern.compile("%(?:\\d+\\$)?(?:[-#+ 0,\\(<]*)?(?:\\d+)?(?:\\.\\d+)?([tT]?[a-zA-Z%])");
+
+    private void checkFormattedMethod(DetailAST ast) {
+        final DetailAST dotAst = ast.findFirstToken(TokenTypes.DOT);
+        if (dotAst == null) {
+            return;
+        }
+
+        final String methodName = dotAst.findFirstToken(TokenTypes.IDENT).getText();
+        if (methodName.equals("formatted") == false) {
+            return;
+        }
+
+        final DetailAST subjectAst = dotAst.getFirstChild();
+
+        String stringContent = null;
+        if (subjectAst.getType() == TokenTypes.TEXT_BLOCK_LITERAL_BEGIN) {
+            stringContent = subjectAst.findFirstToken(TokenTypes.TEXT_BLOCK_CONTENT).getText();
+        } else if (subjectAst.getType() == TokenTypes.STRING_LITERAL) {
+            stringContent = subjectAst.getText();
+        }
+
+        if (stringContent != null) {
+            final Matcher m = formatSpecifier.matcher(stringContent);
+            while (m.find()) {
+                char specifier = m.group(1).toLowerCase(Locale.ROOT).charAt(0);
+
+                if (specifier == 'd' || specifier == 'e' || specifier == 'f' || specifier == 'g' || specifier == 't') {
+                    log(ast, FORMATTED_MSG_KEY, m.group());
+                }
+            }
+        }
+    }
+}
diff --git a/build-tools-internal/src/main/resources/checkstyle.xml b/build-tools-internal/src/main/resources/checkstyle.xml
index 95a32e026c1ff..22a0d2912e4d7 100644
--- a/build-tools-internal/src/main/resources/checkstyle.xml
+++ b/build-tools-internal/src/main/resources/checkstyle.xml
@@ -130,6 +130,12 @@
     </module>
     -->
 
+    <module name="org.elasticsearch.gradle.internal.checkstyle.StringFormattingCheck">
+        <message
+            key="forbidden.formatted"
+            value="''{0}'' format specifier is unsafe inside ''.formatted'' calls, as it uses the default locale. Use ''String.format'' for numeric formatting with ''Locale.ROOT'' instead." />
+    </module>
+
     <!-- We don't use Java's builtin serialization and we suppress all warning
       about it. The flip side of that coin is that we shouldn't _try_ to use
       it. We can't outright ban it with ForbiddenApis because it complain about
diff --git a/build-tools-internal/src/main/resources/forbidden/es-server-signatures.txt b/build-tools-internal/src/main/resources/forbidden/es-server-signatures.txt
index 258ee0840737f..68769530a5c88 100644
--- a/build-tools-internal/src/main/resources/forbidden/es-server-signatures.txt
+++ b/build-tools-internal/src/main/resources/forbidden/es-server-signatures.txt
@@ -130,3 +130,7 @@ org.apache.logging.log4j.Logger#error(java.lang.Object)
 org.apache.logging.log4j.Logger#error(java.lang.Object, java.lang.Throwable)
 org.apache.logging.log4j.Logger#fatal(java.lang.Object)
 org.apache.logging.log4j.Logger#fatal(java.lang.Object, java.lang.Throwable)
+
+# This is permitted in test code, where we have a Checkstyle rule to guard
+# against unsafe uses. This leniency does not extend to server code.
+java.lang.String#formatted(java.lang.Object[]) @ Uses default locale - use String#format(Locale, String, Object...) instead
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/indices/IndicesLifecycleListenerIT.java b/server/src/internalClusterTest/java/org/elasticsearch/indices/IndicesLifecycleListenerIT.java
index 5266e73c9126e..b999487a1ce5e 100644
--- a/server/src/internalClusterTest/java/org/elasticsearch/indices/IndicesLifecycleListenerIT.java
+++ b/server/src/internalClusterTest/java/org/elasticsearch/indices/IndicesLifecycleListenerIT.java
@@ -35,6 +35,7 @@
 import java.util.Arrays;
 import java.util.Collection;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentMap;
@@ -244,11 +245,11 @@ private static void assertShardStatesMatch(
         try {
             assertBusy(waitPredicate, 1, TimeUnit.MINUTES);
         } catch (AssertionError ae) {
-            fail("""
+            fail(String.format(Locale.ROOT, """
                 failed to observe expect shard states
                 expected: [%d] shards with states: %s
                 observed:
-                %s""".formatted(numShards, Strings.arrayToCommaDelimitedString(shardStates), stateChangeListener));
+                %s""", numShards, Strings.arrayToCommaDelimitedString(shardStates), stateChangeListener));
         }
 
         stateChangeListener.shardStates.clear();
diff --git a/server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java b/server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java
index 176e01f931fe6..e079603cf02d6 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/KeywordFieldMapper.java
@@ -52,6 +52,7 @@
 import java.io.UncheckedIOException;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
 import java.util.function.Supplier;
@@ -636,17 +637,17 @@ private static String normalizeValue(NamedAnalyzer normalizer, String field, Str
             final CharTermAttribute termAtt = ts.addAttribute(CharTermAttribute.class);
             ts.reset();
             if (ts.incrementToken() == false) {
-                throw new IllegalStateException("""
+                throw new IllegalStateException(String.format(Locale.ROOT, """
                     The normalization token stream is expected to produce exactly 1 token, \
                     but got 0 for analyzer %s and input "%s"
-                    """.formatted(normalizer, value));
+                    """, normalizer, value));
             }
             final String newValue = termAtt.toString();
             if (ts.incrementToken()) {
-                throw new IllegalStateException("""
+                throw new IllegalStateException(String.format(Locale.ROOT, """
                     The normalization token stream is expected to produce exactly 1 token, \
                     but got 2+ for analyzer %s and input "%s"
-                    """.formatted(normalizer, value));
+                    """, normalizer, value));
             }
             ts.end();
             return newValue;
diff --git a/server/src/main/java/org/elasticsearch/indices/SystemIndices.java b/server/src/main/java/org/elasticsearch/indices/SystemIndices.java
index fe520258b63fb..47501f66bb3b6 100644
--- a/server/src/main/java/org/elasticsearch/indices/SystemIndices.java
+++ b/server/src/main/java/org/elasticsearch/indices/SystemIndices.java
@@ -40,6 +40,7 @@
 import java.util.Comparator;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.Optional;
@@ -644,7 +645,9 @@ Collection<SystemIndexDescriptor> getSystemIndexDescriptors() {
     public static void validateFeatureName(String name, String plugin) {
         if (SnapshotsService.NO_FEATURE_STATES_VALUE.equalsIgnoreCase(name)) {
             throw new IllegalArgumentException(
-                "feature name cannot be reserved name [\"%s\"], but was for plugin [%s]".formatted(
+                String.format(
+                    Locale.ROOT,
+                    "feature name cannot be reserved name [\"%s\"], but was for plugin [%s]",
                     SnapshotsService.NO_FEATURE_STATES_VALUE,
                     plugin
                 )
diff --git a/server/src/main/java/org/elasticsearch/search/aggregations/bucket/BucketsAggregator.java b/server/src/main/java/org/elasticsearch/search/aggregations/bucket/BucketsAggregator.java
index 3b310d78483a6..1861cbe7c9551 100644
--- a/server/src/main/java/org/elasticsearch/search/aggregations/bucket/BucketsAggregator.java
+++ b/server/src/main/java/org/elasticsearch/search/aggregations/bucket/BucketsAggregator.java
@@ -30,6 +30,7 @@
 import java.util.Arrays;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
@@ -406,9 +407,9 @@ public BucketComparator bucketComparator(String key, SortOrder order) {
         if (key == null || "doc_count".equals(key)) {
             return (lhs, rhs) -> order.reverseMul() * Long.compare(bucketDocCount(lhs), bucketDocCount(rhs));
         }
-        throw new IllegalArgumentException("""
+        throw new IllegalArgumentException(String.format(Locale.ROOT, """
             Ordering on a single-bucket aggregation can only be done on its doc_count. \
-            Either drop the key (a la "%s") or change it to "doc_count" (a la "%s.doc_count") or "key".""".formatted(name(), name()));
+            Either drop the key (a la "%s") or change it to "doc_count" (a la "%s.doc_count") or "key".""", name(), name()));
     }
 
     public static boolean descendsFromGlobalAggregator(Aggregator parent) {
diff --git a/server/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/heuristic/NXYSignificanceHeuristic.java b/server/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/heuristic/NXYSignificanceHeuristic.java
index 31918cfb7042a..0e1ee25051ab1 100644
--- a/server/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/heuristic/NXYSignificanceHeuristic.java
+++ b/server/src/main/java/org/elasticsearch/search/aggregations/bucket/terms/heuristic/NXYSignificanceHeuristic.java
@@ -15,6 +15,7 @@
 import org.elasticsearch.xcontent.XContentBuilder;
 
 import java.io.IOException;
+import java.util.Locale;
 import java.util.function.BiFunction;
 import java.util.function.Function;
 
@@ -26,9 +27,9 @@ public abstract class NXYSignificanceHeuristic extends SignificanceHeuristic {
 
     protected static final ParseField INCLUDE_NEGATIVES_FIELD = new ParseField("include_negatives");
 
-    protected static final String SCORE_ERROR_MESSAGE = """
+    protected static final String SCORE_ERROR_MESSAGE = String.format(Locale.ROOT, """
         , does your background filter not include all documents in the bucket? If so and it is intentional, set "%s": false
-        """.formatted(BACKGROUND_IS_SUPERSET.getPreferredName());
+        """, BACKGROUND_IS_SUPERSET.getPreferredName());
 
     protected final boolean backgroundIsSuperset;
 
diff --git a/server/src/main/java/org/elasticsearch/search/aggregations/metrics/NumericMetricsAggregator.java b/server/src/main/java/org/elasticsearch/search/aggregations/metrics/NumericMetricsAggregator.java
index c35e521b3feea..7853422daac2c 100644
--- a/server/src/main/java/org/elasticsearch/search/aggregations/metrics/NumericMetricsAggregator.java
+++ b/server/src/main/java/org/elasticsearch/search/aggregations/metrics/NumericMetricsAggregator.java
@@ -13,6 +13,7 @@
 import org.elasticsearch.search.sort.SortOrder;
 
 import java.io.IOException;
+import java.util.Locale;
 import java.util.Map;
 
 public abstract class NumericMetricsAggregator extends MetricsAggregator {
@@ -33,9 +34,9 @@ protected SingleValue(String name, AggregationContext context, Aggregator parent
         @Override
         public BucketComparator bucketComparator(String key, SortOrder order) {
             if (key != null && false == "value".equals(key)) {
-                throw new IllegalArgumentException("""
+                throw new IllegalArgumentException(String.format(Locale.ROOT, """
                     Ordering on a single-value metrics aggregation can only be done on its value. \
-                    Either drop the key (a la "%s") or change it to "value" (a la "%s.value")""".formatted(name(), name()));
+                    Either drop the key (a la "%s") or change it to "value" (a la "%s.value")""", name(), name()));
             }
             return (lhs, rhs) -> Comparators.compareDiscardNaN(metric(lhs), metric(rhs), order == SortOrder.ASC);
         }
diff --git a/server/src/main/java/org/elasticsearch/transport/RemoteConnectionStrategy.java b/server/src/main/java/org/elasticsearch/transport/RemoteConnectionStrategy.java
index 99c3ac679eb48..f135e208ad817 100644
--- a/server/src/main/java/org/elasticsearch/transport/RemoteConnectionStrategy.java
+++ b/server/src/main/java/org/elasticsearch/transport/RemoteConnectionStrategy.java
@@ -431,7 +431,9 @@ public void validate(T value, Map<Setting<?>, Object> settings, boolean isPresen
             ConnectionStrategy modeType = (ConnectionStrategy) settings.get(concrete);
             if (isPresent && modeType.equals(expectedStrategy) == false) {
                 throw new IllegalArgumentException(
-                    "Setting \"%s\" cannot be used with the configured \"%s\" [required=%s, configured=%s]".formatted(
+                    String.format(
+                        Locale.ROOT,
+                        "Setting \"%s\" cannot be used with the configured \"%s\" [required=%s, configured=%s]",
                         key,
                         concrete.getKey(),
                         expectedStrategy.name(),
diff --git a/server/src/test/java/org/elasticsearch/ingest/PipelineConfigurationTests.java b/server/src/test/java/org/elasticsearch/ingest/PipelineConfigurationTests.java
index 97676f7837c09..6458c89ee492f 100644
--- a/server/src/test/java/org/elasticsearch/ingest/PipelineConfigurationTests.java
+++ b/server/src/test/java/org/elasticsearch/ingest/PipelineConfigurationTests.java
@@ -24,6 +24,7 @@
 
 import java.io.IOException;
 import java.nio.charset.StandardCharsets;
+import java.util.Locale;
 import java.util.function.Predicate;
 
 import static org.hamcrest.Matchers.equalTo;
@@ -98,9 +99,9 @@ public void testGetVersion() {
         {
             // null version
             int version = randomInt();
-            String configJson = """
+            String configJson = String.format(Locale.ROOT, """
                 {"version": %d, "description": "blah", "_meta" : {"foo": "bar"}}
-                """.formatted(version);
+                """, version);
             PipelineConfiguration configuration = new PipelineConfiguration(
                 "1",
                 new BytesArray(configJson.getBytes(StandardCharsets.UTF_8)),
diff --git a/test/framework/src/main/java/org/elasticsearch/test/rest/yaml/section/ClientYamlTestSuite.java b/test/framework/src/main/java/org/elasticsearch/test/rest/yaml/section/ClientYamlTestSuite.java
index fc7d505d89329..38fe230539e2e 100644
--- a/test/framework/src/main/java/org/elasticsearch/test/rest/yaml/section/ClientYamlTestSuite.java
+++ b/test/framework/src/main/java/org/elasticsearch/test/rest/yaml/section/ClientYamlTestSuite.java
@@ -24,6 +24,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Objects;
 import java.util.Set;
 import java.util.TreeSet;
@@ -167,10 +168,10 @@ private static Stream<String> validateExecutableSections(
             .map(section -> (DoSection) section)
             .filter(section -> false == section.getExpectedWarningHeaders().isEmpty())
             .filter(section -> false == hasSkipFeature("warnings", testSection, setupSection, teardownSection))
-            .map(section -> """
+            .map(section -> String.format(Locale.ROOT, """
                 attempted to add a [do] with a [warnings] section without a corresponding ["skip": "features": "warnings"] \
                 so runners that do not support the [warnings] section can skip the test at line [%d]\
-                """.formatted(section.getLocation().lineNumber));
+                """, section.getLocation().lineNumber));
 
         errors = Stream.concat(
             errors,
@@ -179,11 +180,11 @@ private static Stream<String> validateExecutableSections(
                 .map(section -> (DoSection) section)
                 .filter(section -> false == section.getExpectedWarningHeadersRegex().isEmpty())
                 .filter(section -> false == hasSkipFeature("warnings_regex", testSection, setupSection, teardownSection))
-                .map(section -> """
+                .map(section -> String.format(Locale.ROOT, """
                     attempted to add a [do] with a [warnings_regex] section without a corresponding \
                     ["skip": "features": "warnings_regex"] so runners that do not support the [warnings_regex] \
                     section can skip the test at line [%d]\
-                    """.formatted(section.getLocation().lineNumber))
+                    """, section.getLocation().lineNumber))
         );
 
         errors = Stream.concat(
@@ -193,11 +194,11 @@ private static Stream<String> validateExecutableSections(
                 .map(section -> (DoSection) section)
                 .filter(section -> false == section.getAllowedWarningHeaders().isEmpty())
                 .filter(section -> false == hasSkipFeature("allowed_warnings", testSection, setupSection, teardownSection))
-                .map(section -> """
+                .map(section -> String.format(Locale.ROOT, """
                     attempted to add a [do] with a [allowed_warnings] section without a corresponding \
                     ["skip": "features": "allowed_warnings"] so runners that do not support the [allowed_warnings] \
                     section can skip the test at line [%d]\
-                    """.formatted(section.getLocation().lineNumber))
+                    """, section.getLocation().lineNumber))
         );
 
         errors = Stream.concat(
@@ -207,11 +208,11 @@ private static Stream<String> validateExecutableSections(
                 .map(section -> (DoSection) section)
                 .filter(section -> false == section.getAllowedWarningHeadersRegex().isEmpty())
                 .filter(section -> false == hasSkipFeature("allowed_warnings_regex", testSection, setupSection, teardownSection))
-                .map(section -> """
+                .map(section -> String.format(Locale.ROOT, """
                     attempted to add a [do] with a [allowed_warnings_regex] section without a corresponding \
                     ["skip": "features": "allowed_warnings_regex"] so runners that do not support the [allowed_warnings_regex] \
                     section can skip the test at line [%d]\
-                    """.formatted(section.getLocation().lineNumber))
+                    """, section.getLocation().lineNumber))
         );
 
         errors = Stream.concat(
@@ -221,11 +222,11 @@ private static Stream<String> validateExecutableSections(
                 .map(section -> (DoSection) section)
                 .filter(section -> NodeSelector.ANY != section.getApiCallSection().getNodeSelector())
                 .filter(section -> false == hasSkipFeature("node_selector", testSection, setupSection, teardownSection))
-                .map(section -> """
+                .map(section -> String.format(Locale.ROOT, """
                     attempted to add a [do] with a [node_selector] section without a corresponding \
                     ["skip": "features": "node_selector"] so runners that do not support the [node_selector] section \
                     can skip the test at line [%d]\
-                    """.formatted(section.getLocation().lineNumber))
+                    """, section.getLocation().lineNumber))
         );
 
         errors = Stream.concat(
@@ -233,10 +234,10 @@ private static Stream<String> validateExecutableSections(
             sections.stream()
                 .filter(section -> section instanceof ContainsAssertion)
                 .filter(section -> false == hasSkipFeature("contains", testSection, setupSection, teardownSection))
-                .map(section -> """
+                .map(section -> String.format(Locale.ROOT, """
                     attempted to add a [contains] assertion without a corresponding ["skip": "features": "contains"] \
                     so runners that do not support the [contains] assertion can skip the test at line [%d]\
-                    """.formatted(section.getLocation().lineNumber))
+                    """, section.getLocation().lineNumber))
         );
 
         errors = Stream.concat(
@@ -246,10 +247,10 @@ private static Stream<String> validateExecutableSections(
                 .map(section -> (DoSection) section)
                 .filter(section -> false == section.getApiCallSection().getHeaders().isEmpty())
                 .filter(section -> false == hasSkipFeature("headers", testSection, setupSection, teardownSection))
-                .map(section -> """
+                .map(section -> String.format(Locale.ROOT, """
                     attempted to add a [do] with a [headers] section without a corresponding ["skip": "features": "headers"] \
                     so runners that do not support the [headers] section can skip the test at line [%d]\
-                    """.formatted(section.getLocation().lineNumber))
+                    """, section.getLocation().lineNumber))
         );
 
         errors = Stream.concat(
@@ -257,10 +258,10 @@ private static Stream<String> validateExecutableSections(
             sections.stream()
                 .filter(section -> section instanceof CloseToAssertion)
                 .filter(section -> false == hasSkipFeature("close_to", testSection, setupSection, teardownSection))
-                .map(section -> """
+                .map(section -> String.format(Locale.ROOT, """
                     attempted to add a [close_to] assertion without a corresponding ["skip": "features": "close_to"] \
                     so runners that do not support the [close_to] assertion can skip the test at line [%d]\
-                    """.formatted(section.getLocation().lineNumber))
+                    """, section.getLocation().lineNumber))
         );
 
         return errors;
diff --git a/test/framework/src/test/java/org/elasticsearch/test/rest/yaml/section/ClientYamlTestSuiteTests.java b/test/framework/src/test/java/org/elasticsearch/test/rest/yaml/section/ClientYamlTestSuiteTests.java
index 6f54d5f103f92..82ec30b74d5c4 100644
--- a/test/framework/src/test/java/org/elasticsearch/test/rest/yaml/section/ClientYamlTestSuiteTests.java
+++ b/test/framework/src/test/java/org/elasticsearch/test/rest/yaml/section/ClientYamlTestSuiteTests.java
@@ -17,6 +17,7 @@
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.regex.Pattern;
 
@@ -448,11 +449,11 @@ public void testAddingDoWithWarningWithoutSkipWarnings() {
         doSection.setApiCallSection(new ApiCallSection("test"));
         ClientYamlTestSuite testSuite = createTestSuite(SkipSection.EMPTY, doSection);
         Exception e = expectThrows(IllegalArgumentException.class, testSuite::validate);
-        assertThat(e.getMessage(), containsString("""
+        assertThat(e.getMessage(), containsString(String.format(Locale.ROOT, """
             api/name:
             attempted to add a [do] with a [warnings] section without a corresponding ["skip": "features": "warnings"] \
             so runners that do not support the [warnings] section can skip the test at line [%d]\
-            """.formatted(lineNumber)));
+            """, lineNumber)));
     }
 
     public void testAddingDoWithWarningRegexWithoutSkipWarnings() {
@@ -462,11 +463,11 @@ public void testAddingDoWithWarningRegexWithoutSkipWarnings() {
         doSection.setApiCallSection(new ApiCallSection("test"));
         ClientYamlTestSuite testSuite = createTestSuite(SkipSection.EMPTY, doSection);
         Exception e = expectThrows(IllegalArgumentException.class, testSuite::validate);
-        assertThat(e.getMessage(), containsString("""
+        assertThat(e.getMessage(), containsString(String.format(Locale.ROOT, """
             api/name:
             attempted to add a [do] with a [warnings_regex] section without a corresponding ["skip": "features": "warnings_regex"] \
             so runners that do not support the [warnings_regex] section can skip the test at line [%d]\
-            """.formatted(lineNumber)));
+            """, lineNumber)));
     }
 
     public void testAddingDoWithAllowedWarningWithoutSkipAllowedWarnings() {
@@ -476,12 +477,12 @@ public void testAddingDoWithAllowedWarningWithoutSkipAllowedWarnings() {
         doSection.setApiCallSection(new ApiCallSection("test"));
         ClientYamlTestSuite testSuite = createTestSuite(SkipSection.EMPTY, doSection);
         Exception e = expectThrows(IllegalArgumentException.class, testSuite::validate);
-        assertThat(e.getMessage(), containsString("""
+        assertThat(e.getMessage(), containsString(String.format(Locale.ROOT, """
             api/name:
             attempted to add a [do] with a [allowed_warnings] section without a corresponding ["skip": "features": \
             "allowed_warnings"] so runners that do not support the [allowed_warnings] section can skip the test at \
             line [%d]\
-            """.formatted(lineNumber)));
+            """, lineNumber)));
     }
 
     public void testAddingDoWithAllowedWarningRegexWithoutSkipAllowedWarnings() {
@@ -491,12 +492,12 @@ public void testAddingDoWithAllowedWarningRegexWithoutSkipAllowedWarnings() {
         doSection.setApiCallSection(new ApiCallSection("test"));
         ClientYamlTestSuite testSuite = createTestSuite(SkipSection.EMPTY, doSection);
         Exception e = expectThrows(IllegalArgumentException.class, testSuite::validate);
-        assertThat(e.getMessage(), containsString("""
+        assertThat(e.getMessage(), containsString(String.format(Locale.ROOT, """
             api/name:
             attempted to add a [do] with a [allowed_warnings_regex] section without a corresponding ["skip": "features": \
             "allowed_warnings_regex"] so runners that do not support the [allowed_warnings_regex] section can skip the test \
             at line [%d]\
-            """.formatted(lineNumber)));
+            """, lineNumber)));
     }
 
     public void testAddingDoWithHeaderWithoutSkipHeaders() {
@@ -507,11 +508,11 @@ public void testAddingDoWithHeaderWithoutSkipHeaders() {
         doSection.setApiCallSection(apiCallSection);
         ClientYamlTestSuite testSuite = createTestSuite(SkipSection.EMPTY, doSection);
         Exception e = expectThrows(IllegalArgumentException.class, testSuite::validate);
-        assertThat(e.getMessage(), containsString("""
+        assertThat(e.getMessage(), containsString(String.format(Locale.ROOT, """
             api/name:
             attempted to add a [do] with a [headers] section without a corresponding ["skip": "features": "headers"] \
             so runners that do not support the [headers] section can skip the test at line [%d]\
-            """.formatted(lineNumber)));
+            """, lineNumber)));
     }
 
     public void testAddingDoWithNodeSelectorWithoutSkipNodeSelector() {
@@ -522,11 +523,11 @@ public void testAddingDoWithNodeSelectorWithoutSkipNodeSelector() {
         doSection.setApiCallSection(apiCall);
         ClientYamlTestSuite testSuite = createTestSuite(SkipSection.EMPTY, doSection);
         Exception e = expectThrows(IllegalArgumentException.class, testSuite::validate);
-        assertThat(e.getMessage(), containsString("""
+        assertThat(e.getMessage(), containsString(String.format(Locale.ROOT, """
             api/name:
             attempted to add a [do] with a [node_selector] section without a corresponding ["skip": "features": "node_selector"] \
             so runners that do not support the [node_selector] section can skip the test at line [%d]\
-            """.formatted(lineNumber)));
+            """, lineNumber)));
     }
 
     public void testAddingContainsWithoutSkipContains() {
@@ -538,11 +539,11 @@ public void testAddingContainsWithoutSkipContains() {
         );
         ClientYamlTestSuite testSuite = createTestSuite(SkipSection.EMPTY, containsAssertion);
         Exception e = expectThrows(IllegalArgumentException.class, testSuite::validate);
-        assertThat(e.getMessage(), containsString("""
+        assertThat(e.getMessage(), containsString(String.format(Locale.ROOT, """
             api/name:
             attempted to add a [contains] assertion without a corresponding ["skip": "features": "contains"] \
             so runners that do not support the [contains] assertion can skip the test at line [%d]\
-            """.formatted(lineNumber)));
+            """, lineNumber)));
     }
 
     public void testMultipleValidationErrors() {
@@ -583,7 +584,7 @@ public void testMultipleValidationErrors() {
 
         ClientYamlTestSuite testSuite = new ClientYamlTestSuite("api", "name", SetupSection.EMPTY, TeardownSection.EMPTY, sections);
         Exception e = expectThrows(IllegalArgumentException.class, testSuite::validate);
-        assertEquals("""
+        assertEquals(String.format(Locale.ROOT, """
             api/name:
             attempted to add a [contains] assertion without a corresponding ["skip": "features": "contains"] so runners that \
             do not support the [contains] assertion can skip the test at line [%d],
@@ -592,7 +593,7 @@ public void testMultipleValidationErrors() {
             attempted to add a [do] with a [node_selector] section without a corresponding ["skip": "features": "node_selector"] so \
             runners that do not support the [node_selector] section can skip the test \
             at line [%d]\
-            """.formatted(firstLineNumber, secondLineNumber, thirdLineNumber), e.getMessage());
+            """, firstLineNumber, secondLineNumber, thirdLineNumber), e.getMessage());
     }
 
     public void testAddingDoWithWarningWithSkip() {
diff --git a/x-pack/plugin/ccr/qa/src/main/java/org/elasticsearch/xpack/ccr/ESCCRRestTestCase.java b/x-pack/plugin/ccr/qa/src/main/java/org/elasticsearch/xpack/ccr/ESCCRRestTestCase.java
index ace6414c22041..ed84f36c669e8 100644
--- a/x-pack/plugin/ccr/qa/src/main/java/org/elasticsearch/xpack/ccr/ESCCRRestTestCase.java
+++ b/x-pack/plugin/ccr/qa/src/main/java/org/elasticsearch/xpack/ccr/ESCCRRestTestCase.java
@@ -27,6 +27,7 @@
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 
 import static org.elasticsearch.rest.action.search.RestSearchAction.TOTAL_HITS_AS_INT_PARAM;
@@ -121,9 +122,9 @@ protected static void pauseFollow(RestClient client, String followIndex) throws
 
     protected static void putAutoFollowPattern(String patternName, String remoteCluster, String indexPattern) throws IOException {
         Request putPatternRequest = new Request("PUT", "/_ccr/auto_follow/" + patternName);
-        putPatternRequest.setJsonEntity("""
+        putPatternRequest.setJsonEntity(String.format(Locale.ROOT, """
             {"leader_index_patterns": ["%s"], "remote_cluster": "%s"}
-            """.formatted(indexPattern, remoteCluster));
+            """, indexPattern, remoteCluster));
         assertOK(client().performRequest(putPatternRequest));
     }
 
@@ -175,9 +176,9 @@ protected static void verifyDocuments(final RestClient client, final String inde
 
     protected static void verifyCcrMonitoring(final String expectedLeaderIndex, final String expectedFollowerIndex) throws IOException {
         Request request = new Request("GET", "/.monitoring-*/_search");
-        request.setJsonEntity("""
+        request.setJsonEntity(String.format(Locale.ROOT, """
             {"query": {"term": {"ccr_stats.leader_index": "%s"}}}
-            """.formatted(expectedLeaderIndex));
+            """, expectedLeaderIndex));
         Map<String, ?> response;
         try {
             response = toMap(adminClient().performRequest(request));
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlStatsIndex.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlStatsIndex.java
index 8985c65e679ca..df8edca78a369 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlStatsIndex.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlStatsIndex.java
@@ -15,6 +15,8 @@
 import org.elasticsearch.xpack.core.ml.utils.MlIndexAndAlias;
 import org.elasticsearch.xpack.core.template.TemplateUtils;
 
+import java.util.Locale;
+
 /**
  * Describes the indices where ML is storing various stats about the users jobs.
  */
@@ -27,10 +29,10 @@ public class MlStatsIndex {
     private MlStatsIndex() {}
 
     public static String wrappedMapping() {
-        return """
+        return String.format(Locale.ROOT, """
             {
             "_doc" : %s
-            }""".formatted(mapping());
+            }""", mapping());
     }
 
     public static String mapping() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/persistence/AnomalyDetectorsIndex.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/persistence/AnomalyDetectorsIndex.java
index fb1c9329513ca..c8f8ddfbed43d 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/persistence/AnomalyDetectorsIndex.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/job/persistence/AnomalyDetectorsIndex.java
@@ -18,6 +18,8 @@
 import org.elasticsearch.xpack.core.ml.utils.MlIndexAndAlias;
 import org.elasticsearch.xpack.core.template.TemplateUtils;
 
+import java.util.Locale;
+
 import static org.elasticsearch.xpack.core.ClientHelper.ML_ORIGIN;
 import static org.elasticsearch.xpack.core.ClientHelper.executeAsyncWithOrigin;
 
@@ -125,10 +127,10 @@ public static void createStateIndexAndAliasIfNecessaryAndWaitForYellow(
     }
 
     public static String wrappedResultsMapping() {
-        return """
+        return String.format(Locale.ROOT, """
             {
             "_doc" : %s
-            }""".formatted(resultsMapping());
+            }""", resultsMapping());
     }
 
     public static String resultsMapping() {
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/realm/ClearRealmCacheResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/realm/ClearRealmCacheResponse.java
index f29b3c2ac8464..6a4b6b0843469 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/realm/ClearRealmCacheResponse.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/realm/ClearRealmCacheResponse.java
@@ -20,6 +20,7 @@
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Locale;
 
 public class ClearRealmCacheResponse extends BaseNodesResponse<ClearRealmCacheResponse.Node> implements ToXContentFragment {
 
@@ -63,8 +64,8 @@ public String toString() {
             builder.endObject();
             return Strings.toString(builder);
         } catch (IOException e) {
-            return """
-                { "error" : "%s" }""".formatted(e.getMessage());
+            return String.format(Locale.ROOT, """
+                { "error" : "%s" }""", e.getMessage());
         }
     }
 
diff --git a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/role/ClearRolesCacheResponse.java b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/role/ClearRolesCacheResponse.java
index 79c74e364ac9a..3d5dd488e4264 100644
--- a/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/role/ClearRolesCacheResponse.java
+++ b/x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/action/role/ClearRolesCacheResponse.java
@@ -20,6 +20,7 @@
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Locale;
 
 /**
  * The response object that will be returned when clearing the cache of native roles
@@ -66,8 +67,8 @@ public String toString() {
             builder.endObject();
             return Strings.toString(builder);
         } catch (IOException e) {
-            return """
-                { "error" : "%s" }""".formatted(e.getMessage());
+            return String.format(Locale.ROOT, """
+                { "error" : "%s" }""", e.getMessage());
         }
     }
 
diff --git a/x-pack/plugin/enrich/qa/common/src/main/java/org/elasticsearch/test/enrich/CommonEnrichRestTestCase.java b/x-pack/plugin/enrich/qa/common/src/main/java/org/elasticsearch/test/enrich/CommonEnrichRestTestCase.java
index 8cecfc1eaeac0..1439465a4fc61 100644
--- a/x-pack/plugin/enrich/qa/common/src/main/java/org/elasticsearch/test/enrich/CommonEnrichRestTestCase.java
+++ b/x-pack/plugin/enrich/qa/common/src/main/java/org/elasticsearch/test/enrich/CommonEnrichRestTestCase.java
@@ -22,6 +22,7 @@
 
 import java.io.IOException;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 
@@ -108,10 +109,10 @@ private void setupGenericLifecycleTest(boolean deletePipeilne, String field, Str
 
         // Create pipeline
         Request putPipelineRequest = new Request("PUT", "/_ingest/pipeline/my_pipeline");
-        putPipelineRequest.setJsonEntity("""
+        putPipelineRequest.setJsonEntity(String.format(Locale.ROOT, """
             {
               "processors": [ { "enrich": { "policy_name": "my_policy", "field": "%s", "target_field": "entry" } } ]
-            }""".formatted(field));
+            }""", field));
         assertOK(client().performRequest(putPipelineRequest));
 
         // Index document using pipeline with enrich processor:
@@ -248,7 +249,7 @@ public static void createSourceIndex(String index) throws IOException {
     }
 
     public static String createSourceIndexMapping() {
-        return """
+        return String.format(Locale.ROOT, """
             "properties": {
                 "host": {
                   "type": "keyword"
@@ -282,7 +283,7 @@ public static String createSourceIndexMapping() {
                   "type": "ip_range"
                 }
               }
-            """.formatted(randomBoolean() ? "" : ", \"format\": \"yyyy-MM-dd\"");
+            """, randomBoolean() ? "" : ", \"format\": \"yyyy-MM-dd\"");
     }
 
     protected static Map<String, Object> toMap(Response response) throws IOException {
diff --git a/x-pack/plugin/eql/qa/common/src/main/java/org/elasticsearch/test/eql/EqlRestTestCase.java b/x-pack/plugin/eql/qa/common/src/main/java/org/elasticsearch/test/eql/EqlRestTestCase.java
index ef484fa593e83..c3192c71e7844 100644
--- a/x-pack/plugin/eql/qa/common/src/main/java/org/elasticsearch/test/eql/EqlRestTestCase.java
+++ b/x-pack/plugin/eql/qa/common/src/main/java/org/elasticsearch/test/eql/EqlRestTestCase.java
@@ -17,6 +17,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 
 import static org.elasticsearch.xpack.ql.TestUtils.assertNoSearchContexts;
@@ -40,21 +41,21 @@ public void checkSearchContent() throws Exception {
         { "{}", "query is null or empty" },
         { """
             {"query": ""}""", "query is null or empty" },
-        { """
+        { String.format(Locale.ROOT, """
             {"query": "%s", "timestamp_field": ""}
-            """.formatted(validQuery), "timestamp field is null or empty" },
-        { """
+            """, validQuery), "timestamp field is null or empty" },
+        { String.format(Locale.ROOT, """
             {"query": "%s", "event_category_field": ""}
-            """.formatted(validQuery), "event category field is null or empty" },
-        { """
+            """, validQuery), "event category field is null or empty" },
+        { String.format(Locale.ROOT, """
             {"query": "%s", "size": -1}
-            """.formatted(validQuery), "size must be greater than or equal to 0" },
-        { """
+            """, validQuery), "size must be greater than or equal to 0" },
+        { String.format(Locale.ROOT, """
             {"query": "%s", "filter": null}
-            """.formatted(validQuery), "filter doesn't support values of type: VALUE_NULL" },
-        { """
+            """, validQuery), "filter doesn't support values of type: VALUE_NULL" },
+        { String.format(Locale.ROOT, """
             {"query": "%s", "filter": {}}
-            """.formatted(validQuery), "query malformed, empty clause found" } };
+            """, validQuery), "query malformed, empty clause found" } };
 
     public void testBadRequests() throws Exception {
         createIndex(defaultValidationIndexName, (String) null);
diff --git a/x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/util/Graphviz.java b/x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/util/Graphviz.java
index e4a234cbf5197..9a1b2e9630894 100644
--- a/x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/util/Graphviz.java
+++ b/x-pack/plugin/ql/src/main/java/org/elasticsearch/xpack/ql/util/Graphviz.java
@@ -11,6 +11,7 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Map.Entry;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -25,12 +26,12 @@ public abstract class Graphviz {
     public static String dot(String name, Node<?> root) {
         StringBuilder sb = new StringBuilder();
         // name
-        sb.append("""
+        sb.append(String.format(Locale.ROOT, """
             digraph G { rankdir=BT;
               label="%s";
               node[shape=plaintext, color=azure1];
               edge[color=black,arrowsize=0.5];
-            """.formatted(name));
+            """, name));
         handleNode(sb, root, new AtomicInteger(0), INDENT, true);
         sb.append("}");
         return sb.toString();
@@ -131,9 +132,9 @@ private static void handleNode(StringBuilder output, Node<?> n, AtomicInteger no
             <table border="0" cellborder="1" cellspacing="0">
             """);
         indent(nodeInfo, currentIndent + NODE_LABEL_INDENT);
-        nodeInfo.append("""
+        nodeInfo.append(String.format(Locale.ROOT, """
             <th><td border="0" colspan="2" align="center"><b>%s</b></td></th>
-            """.formatted(n.nodeName()));
+            """, n.nodeName()));
         indent(nodeInfo, currentIndent + NODE_LABEL_INDENT);
 
         List<Object> props = n.nodeProperties();
@@ -178,10 +179,10 @@ private static void handleNode(StringBuilder output, Node<?> n, AtomicInteger no
         // check any subtrees
         if (subTrees.isEmpty() == false) {
             // write nested trees
-            output.append("""
+            output.append(String.format(Locale.ROOT, """
                 subgraph cluster_%s{
                 style=filled; color=white; fillcolor=azure2; label="";
-                """.formatted(thisId));
+                """, thisId));
         }
 
         // write node info
diff --git a/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/TokenService.java b/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/TokenService.java
index e8996062f66aa..78efbb83d73e9 100644
--- a/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/TokenService.java
+++ b/x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/TokenService.java
@@ -126,6 +126,7 @@
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
@@ -175,10 +176,10 @@ public final class TokenService {
     static final int IV_BYTES = 12;
     private static final int VERSION_BYTES = 4;
     private static final String ENCRYPTION_CIPHER = "AES/GCM/NoPadding";
-    private static final String EXPIRED_TOKEN_WWW_AUTH_VALUE = """
-        Bearer realm="%s", error="invalid_token", error_description="The access token expired\"""".formatted(XPackField.SECURITY);
-    private static final String MALFORMED_TOKEN_WWW_AUTH_VALUE = """
-        Bearer realm="%s", error="invalid_token", error_description="The access token is malformed\"""".formatted(XPackField.SECURITY);
+    private static final String EXPIRED_TOKEN_WWW_AUTH_VALUE = String.format(Locale.ROOT, """
+        Bearer realm="%s", error="invalid_token", error_description="The access token expired\"""", XPackField.SECURITY);
+    private static final String MALFORMED_TOKEN_WWW_AUTH_VALUE = String.format(Locale.ROOT, """
+        Bearer realm="%s", error="invalid_token", error_description="The access token is malformed\"""", XPackField.SECURITY);
     private static final BackoffPolicy DEFAULT_BACKOFF = BackoffPolicy.exponentialBackoff();
 
     public static final String THREAD_POOL_NAME = XPackField.SECURITY + "-token-key";
diff --git a/x-pack/plugin/sql/sql-client/src/test/java/org/elasticsearch/xpack/sql/client/RemoteFailureTests.java b/x-pack/plugin/sql/sql-client/src/test/java/org/elasticsearch/xpack/sql/client/RemoteFailureTests.java
index e9af90c99e25e..180ed1302baf9 100644
--- a/x-pack/plugin/sql/sql-client/src/test/java/org/elasticsearch/xpack/sql/client/RemoteFailureTests.java
+++ b/x-pack/plugin/sql/sql-client/src/test/java/org/elasticsearch/xpack/sql/client/RemoteFailureTests.java
@@ -13,6 +13,7 @@
 import java.io.InputStream;
 import java.nio.file.Files;
 import java.util.Arrays;
+import java.util.Locale;
 
 import static java.util.Collections.emptyMap;
 import static java.util.Collections.singletonList;
@@ -154,9 +155,9 @@ public void testTooBig() {
             """);
         int i = 0;
         while (tooBig.length() < RemoteFailure.MAX_RAW_RESPONSE) {
-            tooBig.append("""
+            tooBig.append(String.format(Locale.ROOT, """
                 "%04d" : "lots and lots and lots and lots and lots of words",
-                """.formatted(i++));
+                """, i++));
         }
         tooBig.append("""
               "end" : "lots and lots and lots and lots and lots of words"