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Description

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.

PUBLISHED Reserved 2026-03-17 | Published 2026-03-23 | Updated 2026-03-25 | Assigner GitHub_M




MEDIUM: 5.3CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

Problem types

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

Product status

>= 8.1.0.beta1, < 8.1.2.1
affected

>= 8.0.0.beta1, < 8.0.4.1
affected

< 7.2.3.1
affected

References

github.com/.../rails/security/advisories/GHSA-89vf-4333-qx8v

github.com/...ommit/50d732af3b7c8aaf63cbcca0becbc00279b215b7

github.com/...ommit/6e8a81108001d58043de9e54a06fca58962fc2db

github.com/...ommit/c1ad0e8e1972032f3395853a5e99cea035035beb

github.com/rails/rails/releases/tag/v7.2.3.1

github.com/rails/rails/releases/tag/v8.0.4.1

github.com/rails/rails/releases/tag/v8.1.2.1

cve.org (CVE-2026-33170)

nvd.nist.gov (CVE-2026-33170)

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