Vulnerability · Published Mar 23, 2026 · Assigned by GitHub_M
CVE-2026-33173Rails Active Storage has possible content type bypass via metadata in direct uploads
Medium 5.3
In plain English
A medium-severity security flaw in activestorage from rails. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 34% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | rails | 2:6.1.7.10+dfsg-1~deb12u3 | DEBIAN-CVE-2026-33173 |
| Debian:13 | rails | 2:7.2.2.2+dfsg-2~deb13u2 | DEBIAN-CVE-2026-33173 |
| Debian:14 | rails | 2:7.2.3.1+dfsg-1 | DEBIAN-CVE-2026-33173 |
| RubyGems | activestorage | 8.1.2.1 | GHSA-qcfx-2mfw-w4cg |
| RubyGems | activestorage | 8.0.4.1 | GHSA-qcfx-2mfw-w4cg |
| RubyGems | activestorage | 7.2.3.1 | GHSA-qcfx-2mfw-w4cg |
| Ubuntu:24.04:LTS | rails | no fix listed | UBUNTU-CVE-2026-33173 |
| Ubuntu:25.10 | rails | no fix listed | UBUNTU-CVE-2026-33173 |
| Ubuntu:26.04:LTS | rails | no fix listed | UBUNTU-CVE-2026-33173 |
| Ubuntu:26.10 | rails | no fix listed | UBUNTU-CVE-2026-33173 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| rails | activestorage | >= 8.1.0.beta1, < 8.1.2.1>= 8.0.0.beta1, < 8.0.4.1< 7.2.3.1 |
Weakness: CWE-925 · 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-qcfx-2mfw-w4cg x_refsource_CONFIRM
- https://github.com/rails/rails/commit/707c0f1f41f067fdf96d54e99d43b28dfaae7e53 x_refsource_MISC
- https://github.com/rails/rails/commit/8fcb934caadc79c8cc4ce53287046d0f67005b3e x_refsource_MISC
- https://github.com/rails/rails/commit/d9502f5214e2198245a4c1defe9cd02a7c8057d0 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