CVE-2024-53986.yml

---
gem: rails-html-sanitizer
framework: rails
cve: 2024-53986
ghsa: 638j-pmjw-jq48
url: https://github.com/rails/rails-html-sanitizer/security/advisories/GHSA-638j-pmjw-jq48
title: rails-html-sanitizer has XSS vulnerability with certain configurations
date: 2024-12-02
description: |
  ## Summary

  There is a possible XSS vulnerability with certain configurations of
  Rails::HTML::Sanitizer 1.6.0 when used with Rails >= 7.1.0.

  * Versions affected: 1.6.0
  * Not affected: < 1.6.0
  * Fixed versions: 1.6.1

  ## Impact

  A possible XSS vulnerability with certain configurations of
  Rails::HTML::Sanitizer may allow an attacker to inject content if
  HTML5 sanitization is enabled and the application developer has
  overridden the sanitizer's allowed tags in the following way:

  - the "math" and "style" elements are both explicitly allowed

  Code is only impacted if Rails is configured to use HTML5 sanitization,
  please see documentation for
  [`config.action_view.sanitizer_vendor`](https://guides.rubyonrails.org/configuring.html#config-action-view-sanitizer-vendor)
  and [`config.action_text.sanitizer_vendor`](https://guides.rubyonrails.org/configuring.html#config-action-text-sanitizer-vendor)
  for more information on these configuration options.

  The default configuration is to disallow these elements. Code is only
  impacted if allowed tags are being overridden. Applications may be
  doing this in a few different ways:

  1. using application configuration to configure Action View sanitizers'
     allowed tags:

    ```ruby
    # In config/application.rb
    config.action_view.sanitized_allowed_tags = ["math", "style"]
    ```

    see https://guides.rubyonrails.org/configuring.html#configuring-action-view

  2. using a `:tags` option to the Action View helper `sanitize`:

    ```
    <= sanitize @comment.body, tags: ["math", "style"]>
    ```

    see https://api.rubyonrails.org/classes/ActionView/Helpers/SanitizeHelper.html#method-i-sanitize

  3. setting Rails::HTML5::SafeListSanitizer class attribute `allowed_tags`:

    ```ruby
    # class-level option
    Rails::HTML5::SafeListSanitizer.allowed_tags = ["math", "style"]
    ```

    (note that this class may also be referenced as
    `Rails::Html::SafeListSanitizer`)

  4. using a `:tags` options to the Rails::HTML5::SafeListSanitizer
     instance method `sanitize`:

    ```ruby
    # instance-level option
    Rails::HTML5::SafeListSanitizer.new.sanitize(@article.body, tags: ["math", "style"])
    ```

    (note that this class may also be referenced as
     `Rails::Html::SafeListSanitizer`)

  5. setting ActionText::ContentHelper module attribute `allowed_tags`:

    ```ruby
    ActionText::ContentHelper.allowed_tags = ["math", "style"]
    ```

  All users overriding the allowed tags by any of the above mechanisms
  to include both "math" and "style" should either upgrade or use one
  of the workarounds.

  ## Workarounds

  Any one of the following actions will work around this issue:

  - Remove "math" or "style" from the overridden allowed tags,
  - Or, downgrade sanitization to HTML4 (see documentation for
    [`config.action_view.sanitizer_vendor`](https://guides.rubyonrails.org/configuring.html#config-action-view-sanitizer-vendor)
    and [`config.action_text.sanitizer_vendor`](https://guides.rubyonrails.org/configuring.html#config-action-text-sanitizer-vendor)
    for more information).

  ## References

  - [CWE - CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (4.9)](https://cwe.mitre.org/data/definitions/79.html)
  - Original report: https://hackerone.com/reports/2519941

  ## Credit

  This vulnerability was responsibly reported by So Sakaguchi (mokusou).
cvss_v4: 2.3
unaffected_versions:
  - "< 1.6.0"
patched_versions:
  - ">= 1.6.1"
related:
  url:
    - https://nvd.nist.gov/vuln/detail/CVE-2024-53986
    - https://github.com/rails/rails-html-sanitizer/blob/v1.6.1/CHANGELOG.md
    - https://github.com/rails/rails-html-sanitizer/security/advisories/GHSA-638j-pmjw-jq48
    - https://github.com/rails/rails-html-sanitizer/commit/f02ffbb8465e73920b6de0da940f5530f855965e
    - https://github.com/advisories/GHSA-638j-pmjw-jq48