Vulnerability · Published Mar 23, 2026 · Assigned by GitHub_M
CVE-2026-33170Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
Medium 5.3
In plain English
A medium-severity cross-site scripting in activesupport from rails. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | rails | 2:6.1.7.10+dfsg-1~deb12u3 | DEBIAN-CVE-2026-33170 |
| Debian:13 | rails | 2:7.2.2.2+dfsg-2~deb13u2 | DEBIAN-CVE-2026-33170 |
| Debian:14 | rails | 2:7.2.3.1+dfsg-1 | DEBIAN-CVE-2026-33170 |
| RubyGems | activesupport | 8.1.2.1 | GHSA-89vf-4333-qx8v |
| RubyGems | activesupport | 8.0.4.1 | GHSA-89vf-4333-qx8v |
| RubyGems | activesupport | 7.2.3.1 | GHSA-89vf-4333-qx8v |
| Ubuntu:24.04:LTS | rails | no fix listed | UBUNTU-CVE-2026-33170 |
| Ubuntu:25.10 | rails | no fix listed | UBUNTU-CVE-2026-33170 |
| Ubuntu:26.04:LTS | rails | no fix listed | UBUNTU-CVE-2026-33170 |
| Ubuntu:26.10 | rails | no fix listed | UBUNTU-CVE-2026-33170 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| rails | activesupport | >= 8.1.0.beta1, < 8.1.2.1>= 8.0.0.beta1, < 8.0.4.1< 7.2.3.1 |
Weakness: CWE-79 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
References
- https://github.com/rails/rails/security/advisories/GHSA-89vf-4333-qx8v x_refsource_CONFIRM
- https://github.com/rails/rails/commit/50d732af3b7c8aaf63cbcca0becbc00279b215b7 x_refsource_MISC
- https://github.com/rails/rails/commit/6e8a81108001d58043de9e54a06fca58962fc2db x_refsource_MISC
- https://github.com/rails/rails/commit/c1ad0e8e1972032f3395853a5e99cea035035beb x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v7.2.3.1 x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v8.0.4.1 x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v8.1.2.1 x_refsource_MISC