v0.5.6

What's Changed

🔒 Security Fix

Fixes CVE-2025-25186 (GHSA-7fc5-f82f-cx69): A malicious server can exhaust client memory by sending APPENDUID or COPYUID responses with very large uid-set ranges. Net::IMAP::UIDPlusData expands these ranges into arrays of integers.

Fix with minor API changes

Set config.parser_use_deprecated_uidplus_data to false to replace UIDPlusData with AppendUIDData and CopyUIDData. These classes store their UIDs as Net::IMAP::SequenceSet objects (not expanded into arrays of integers). Code that does not handle APPENDUID or COPYUID responses should not see any difference. Code that does handle these responses may need to be updated.

For v0.3.8, this option is not available
For v0.4.19, the default value is true.
For v0.5.6, the default value is :up_to_max_size.
For v0.6.0, the only allowed value will be false (UIDPlusData will be removed from v0.6).

Mitigate with backward compatible API

Adjust config.parser_max_deprecated_uidplus_data_size to limit the maximum UIDPlusData UID set size.
When config.parser_use_deprecated_uidplus_data == true, larger sets will crash.
When config.parser_use_deprecated_uidplus_data == :up_to_max_size, larger sets will use AppendUIDData or CopyUIDData.

For v0.3,8, this limit is hard-coded to 10,000.
For v0.4.19, this limit defaults to 1000.
For v0.5.6, this limit defaults to 100.
For v0.6.0, the only allowed value will be 0 (UIDPlusData will be removed from v0.6).

Please Note: unhandled responses

If the client does not add response handlers to prune unhandled responses, a malicious server can still eventually exhaust all client memory, by repeatedly sending malicious responses. However, net-imap has always retained unhandled responses, and it has always been necessary for long-lived connections to prune these responses. This is not significantly different from connecting to a trusted server with a long-lived connection. To limit the maximum number of retained responses, a simple handler might look something like the following:

limit = 1000
imap.add_response_handler do |resp|
  next unless resp.respond_to?(:name) && resp.respond_to?(:data)
  name = resp.name
  code = resp.data.code&.name if resp.data.is_a?(Net::IMAP::ResponseText)
  imap.responses(name) { _1.slice!(0...-limit) }
  imap.responses(code) { _1.slice!(0...-limit) }
end

Added

• 🔧 Ensure ResponseParser config is mutable and non-global by @nevans in #381
• ✨ Add SequenceSet methods for querying about duplicates by @nevans in #384
• ✨ Add SequenceSet#each_ordered_number by @nevans in #386
• ✨ Add SequenceSet#find_ordered_index by @nevans in #396
• ✨ Add SequenceSet#ordered_at by @nevans in #397
• ✨ Add AppendUIDData and CopyUIDData classes by @nevans in #400
• 🔧 Add parser config for APPENDUID/COPYUID, 🗑️ Deprecate UIDPlusData by @nevans in #401

Fixed

• 🐛 Fix SequenceSet#append when its @string is nil by @nevans in #376
• 🐛 Fix SequenceSet merging in another SequenceSet by @nevans in #377
• 🐛 Fix SequenceSet count dups with multiple "*" by @nevans in #387
• 🥅 Re-raise #starttls error from receiver thread by @nevans in #395

Documentation

• 📚 Fix SequenceSet#cover? documentation by @nevans in #379
• 📚 Document COPYUID in tagged vs untagged responses by @nevans in #398

Other Changes

• 🚚 Move UIDPlusData to its own file by @nevans in #391
• ♻️ Parse uid-set as sequence-set without * by @nevans in #393

Miscellaneous

• ⬆️ Bump step-security/harden-runner from 2.10.2 to 2.10.3 by @dependabot in #375
• ⬆️ Bump step-security/harden-runner from 2.10.3 to 2.10.4 by @dependabot in #380
• ✅ Improve test coverage for SequenceSet enums by @nevans in #383
• ♻️✅ Refactor SequenceSet enumerator tests by @nevans in #385
• ➕ Add "irb" to Gemfile to silence warning by @nevans in #388
• Omit flaky test with macOS platform by @hsbt in #389
• ✅ Improve UIDPlusData test coverage by @nevans in #392
• 🚚 Rename UIDPLUS test file for consistency by @nevans in #399

Full Changelog: v0.5.5...v0.5.6