[CVE-2026-33169] Possible ReDoS vulnerability in number_to_delimited in Active Support

[jhawthorn (John Hawthorn)]

Impact

NumberToDelimitedConverter used a regular expression with gsub! to insert thousands delimiters. This could produce quadratic time complexity on long digit strings.

Releases

The fixed releases are available at the normal locations.

• CVE-2026-33169
• GHSA-cg4j-q9v8-6v38

Versions affected

• activesupport >= 8.1, < 8.1.2.1 (patched in 8.1.2.1)
• activesupport >= 8.0, < 8.0.4.1 (patched in 8.0.4.1)
• activesupport < 7.2.3.1 (patched in 7.2.3.1)

Patches

• 8.1 - https://github.com/rails/rails/commit/ec1a0e215efd27a3b3911aae6df978a80f456a49.patch
• 8.0 - https://github.com/rails/rails/commit/29154f1097da13d48fdb3200760b3e3da66dcb11.patch
• 7.2 - https://github.com/rails/rails/commit/b54a4b373c6f042cab6ee2033246b1c9ecc38974.patch