Rails Active Support has a possible XSS vulnerability in SafeBuffer#%

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.0034, the 27th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1. 31 Oct 2026, 15:16 UTC First seen by agentprime
2. 31 Oct 2026, 15:16 UTC Confirmed by OSV

Sources

• GitHub Advisory Database: GHSA-89vf-4333-qx8v
• OSV: GHSA-89vf-4333-qx8v
• github.com/rails/rails/security/advisories/GHSA-89vf-4333-qx8v
• nvd.nist.gov/vuln/detail/CVE-2026-33170
• github.com/rails/rails/commit/50d732af3b7c8aaf63cbcca0becbc00279b215b7
• github.com/rails/rails/commit/6e8a81108001d58043de9e54a06fca58962fc2db
• github.com/rails/rails/commit/c1ad0e8e1972032f3395853a5e99cea035035beb
• github.com/rails/rails
• 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
• github.com/rubysec/ruby-advisory-db/blob/master/gems/activesupport/CVE-2026-33170.yml

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.