CVE-2026-33170 PUBLISHED

Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, SafeBuffer#% does not propagate the @html_unsafe flag to the newly created buffer. If a SafeBuffer is mutated in place (e.g. via gsub!) and then formatted with % using untrusted arguments, the result incorrectly reports html_safe? == true, bypassing ERB auto-escaping and possibly leading to XSS. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.

• https://github.com/rails/rails/security/advisories/GHSA-89vf-4333-qx8v
• https://github.com/rails/rails/commit/50d732af3b7c8aaf63cbcca0becbc00279b215b7
• https://github.com/rails/rails/commit/6e8a81108001d58043de9e54a06fca58962fc2db
• https://github.com/rails/rails/commit/c1ad0e8e1972032f3395853a5e99cea035035beb
• https://github.com/rails/rails/releases/tag/v7.2.3.1
• https://github.com/rails/rails/releases/tag/v8.0.4.1
• https://github.com/rails/rails/releases/tag/v8.1.2.1

• CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE