# CVE-2026-34830

## Summary

- **CVE ID:** CVE-2026-34830
- **Severity:** MEDIUM
- **CVSS Score:** 5.9 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N)
- **CWE:** CWE-625
- **Published:** Apr 2, 2026
- **Last Modified:** Apr 3, 2026

## Description

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Sendfile#map_accel_path interpolates the value of the X-Accel-Mapping request header directly into a regular expression when rewriting file paths for X-Accel-Redirect. Because the header value is not escaped, an attacker who can supply X-Accel-Mapping to the backend can inject regex metacharacters and control the generated X-Accel-Redirect response header. In deployments using Rack::Sendfile with x-accel-redirect, this can allow an attacker to cause nginx to serve unintended files from configured internal locations. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

## Affected Products

- rack — rack (< 2.2.23)
- rack — rack (>= 3.0.0.beta1, < 3.1.21)
- rack — rack (>= 3.2.0, < 3.2.6)

## References

- [CNA](https://github.com/rack/rack/security/advisories/GHSA-qv7j-4883-hwh7)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.21%
- **EPSS Percentile:** 11.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._