medium6.1
CVE-2026-33170
Active Support is a toolkit of support libraries and Ruby core extensions extracted from the Rails framework.
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| rubygems | activesupport | >= 8.1.0.beta1, < 8.1.2.1 | 8.1.2.1 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Rubyonrails | Rails | before 7.2.3.1 from 8.0.0 before 8.0.4.1 from 8.1.0 before 8.1.2.1 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-89vf-4333-qx8v
- 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
- https://nvd.nist.gov/vuln/detail/CVE-2026-33170
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/activesupport/CVE-2026-33170.yml