CVE-2026-33173: Rails Active Storage has possible content type bypass via metadata in direct uploads

CVE-2026-33173 · Severity: medium · CVSS 4 · Published 2026-03-23

### Impact Active Storage's `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 malicious direct-upload client could set these flags.

### Releases The fixed releases are available at the normal locations.

### Credit This was responsible reported by Hackerone researcher [pwnie](https://hackerone.com/pwnie)

Technologies: activestorage (RubyGems). Vendors: RubyGems.

Quick answers

Is CVE-2026-33173 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-33173 being exploited in the wild.
How severe is CVE-2026-33173?
Medium severity, with a CVSS score of 4, published 23 March 2026.
Which products and versions are affected?
activestorage (RubyGems) ECOSYSTEM:introduced=8.1.0.beta1,fixed=8.1.2.1.
Is there a fix for CVE-2026-33173?
Yes. activestorage (RubyGems): upgrade to 8.1.2.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-33173?
Check whether you run activestorage (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • activestorage (RubyGems): upgrade to 8.1.2.1 or later
    bundle update activestorage

Affected products

  • activestorage (RubyGems) ECOSYSTEM:introduced=8.1.0.beta1,fixed=8.1.2.1

Identifiers

  • CVE-2026-33173
  • GHSA-qcfx-2mfw-w4cg

References

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