Rails Active Storage has possible content type bypass via metadata in direct uploads

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 0.0040, the 34th 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-qcfx-2mfw-w4cg
• OSV: GHSA-qcfx-2mfw-w4cg
• github.com/rails/rails/security/advisories/GHSA-qcfx-2mfw-w4cg
• nvd.nist.gov/vuln/detail/CVE-2026-33173
• github.com/rails/rails/commit/707c0f1f41f067fdf96d54e99d43b28dfaae7e53
• github.com/rails/rails/commit/8fcb934caadc79c8cc4ce53287046d0f67005b3e
• github.com/rails/rails/commit/d9502f5214e2198245a4c1defe9cd02a7c8057d0
• 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/activestorage/CVE-2026-33173.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.