Medium severity · published Mar 23, 2026
CVE-2026-33173
Rails Active Storage has possible content type bypass via metadata in direct uploads
5.3
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 34% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AC
activestorage · rails
>= 8.1.0.beta1, < 8.1.2.1; >= 8.0.0.beta1, < 8.0.4.1; < 7.2.3.1 · source: vendor
RA
Rails · Rubyonrails
before 7.2.3.1; 8.0.0 before 8.0.4.1; 8.1.0 before 8.1.2.1 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33173
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-33173
Patch
https://github.com/rails/rails/commit/707c0f1f41f067fdf96d54e99d43b28dfaae7e53
Patch
https://github.com/rails/rails/commit/8fcb934caadc79c8cc4ce53287046d0f67005b3e
Patch
https://github.com/rails/rails/commit/d9502f5214e2198245a4c1defe9cd02a7c8057d0
Release Notes
https://github.com/rails/rails/releases/tag/v7.2.3.1
Release Notes
https://github.com/rails/rails/releases/tag/v8.0.4.1
Release Notes
https://github.com/rails/rails/releases/tag/v8.1.2.1
More from activestorage
9.8
CVE-2026-33195
Rails Active Storage has possible Path Traversal in DiskService
9.1
CVE-2026-33202
Rails Active Storage has possible glob injection in its DiskService
8.1
CVE-2025-24293
# Active Storage allowed transformation methods potentially unsafe Active Storage attempts to prevent the use of potentially unsafe image transformation methods and parameters…
7.5
CVE-2026-33174
Rails Active Storage has a possible DoS vulnerability when in proxy mode via Range requests
6.5
CVE-2026-33658
Rails Active Storage has a possible DoS vulnerability in proxy mode via multi-range requests