Permissive Regular Expression Affecting rack package, versions <2.2.23>=3.0.0.beta1, <3.1.21>=3.2.0, <3.2.6
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Test your applications- Snyk IDSNYK-RUBY-RACK-15878256
- published3 Apr 2026
- disclosed2 Apr 2026
- creditMehtab Zafar
Introduced: 2 Apr 2026
NewCVE-2026-34830 (opens in a new tab)How to fix?
Upgrade rack to version 2.2.23, 3.1.21, 3.2.6 or higher.
Overview
rack is a minimal, modular and adaptable interface for developing web applications in Ruby. By wrapping HTTP requests and responses in the simplest way possible, it unifies and distills the API for web servers, web frameworks, and software in between (the so-called middleware) into a single method call.
Affected versions of this package are vulnerable to Permissive Regular Expression in the map_accel_path component. An attacker can read arbitrary files by injecting specially crafted values into the HTTP_X_ACCEL_MAPPING header, which are then interpolated into a regular expression and used to rewrite file paths for X-Accel-Redirect responses in nginx.