CVE-2026-33170
Rails Active Support has a possible XSS vulnerability in SafeBuffer#%
- Published
- Updated
- Reserved
- Assigned by
- GitHub_M
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.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_MCNA (assigner) | 4.0 | Medium5.3 | 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 |
| NVDNVD · Analyzed | 4.0 | Medium5.3 | 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X |
- EPSS (exploitation in 30 days)
- 0.34% · top 72% of all CVEs (6 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: partial
The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.3.
Weakness
Affected products
- affected >= 8.1.0.beta1, < 8.1.2.1
- affected >= 8.0.0.beta1, < 8.0.4.1
- affected < 7.2.3.1
Affected packages
From reviewed advisories of the GitHub Advisory Database.
- RubyGemsactivesupportGHSA-89vf-4333-qx8v (opens in a new tab)
References (7)
- https://github.com/rails/rails/security/advisories/GHSA-89vf-4333-qx8v (opens in a new tab)x_refsource_CONFIRM
- https://github.com/rails/rails/commit/50d732af3b7c8aaf63cbcca0becbc00279b215b7 (opens in a new tab)x_refsource_MISC
- https://github.com/rails/rails/commit/6e8a81108001d58043de9e54a06fca58962fc2db (opens in a new tab)x_refsource_MISC
- https://github.com/rails/rails/commit/c1ad0e8e1972032f3395853a5e99cea035035beb (opens in a new tab)x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v7.2.3.1 (opens in a new tab)x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v8.0.4.1 (opens in a new tab)x_refsource_MISC
- https://github.com/rails/rails/releases/tag/v8.1.2.1 (opens in a new tab)x_refsource_MISC
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisory GHSA-89vf-4333-qx8v (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2026-33170)Record last updated .