Vulnerability in Rails Activestorage
CVE-2026-33173
Active Storage allows users to attach cloud and local files in Rails applications. Prior to versions 8.1.2.1, 8.0.4.1, and 7.2.3.1, `DirectUploadsController` accepts arbitrary metadata from the client and persists it on the blob. Because internal flags like `identified` and `analyzed` are stored in the same metadata hash, a direct-upload client can set these flags to skip MIME detection and analysis. This allows an attacker to upload arbitrary content while claiming a safe `content_type`, bypassing any validations that rely on Active Storage's automatic content type identification. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (32.5th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 33rd percentile — 32.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000
Affected products
- Rails Activestorage — versions >= 8.1.0.beta1, < 8.1.2.1, >= 8.0.0.beta1, < 8.0.4.1, < 7.2.3.1
- Rubyonrails Rails
Weakness classification (CWE)
References
- github.com/rails/rails/security/advisories/GHSA-qcfx-2mfw-w4cg (Vendor Advisory)
- github.com/rails/rails/commit/707c0f1f41f067fdf96d54e99d43b28dfaae7e53 (Patch)
- github.com/rails/rails/commit/8fcb934caadc79c8cc4ce53287046d0f67005b3e (Patch)
- github.com/rails/rails/commit/d9502f5214e2198245a4c1defe9cd02a7c8057d0 (Patch)
- github.com/rails/rails/releases/tag/v7.2.3.1 (Release Notes)
- github.com/rails/rails/releases/tag/v8.0.4.1 (Release Notes)
- github.com/rails/rails/releases/tag/v8.1.2.1 (Release Notes)
Frequently asked questions
- What is CVE-2026-33173?
- CVE-2026-33173 is a medium-severity vulnerability in Rails Activestorage, classified under CWE-925. CVSS score: 5.3/10. Published 2026-03-24.
- How severe is CVE-2026-33173?
- Medium severity. CVSS v3 base score is 5.3 out of 10.