CVE-2026-34786 (Medium) detected in rack-2.2.9.gem

Vulnerable Library - rack-2.2.9.gem

Rack provides 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.

Library home page: https://rubygems.org/gems/rack-2.2.9.gem

Path to dependency file: /Gemfile.lock

Path to vulnerable library: /home/wss-scanner/.gem/ruby/3.2.0/cache/rack-2.2.9.gem

Dependency Hierarchy:

• rack-test-2.1.0.gem (Root Library)
  • ❌ rack-2.2.9.gem (Vulnerable Library)

Found in base branch: master

Vulnerability Details

Rack is a modular Ruby web server interface. Prior to versions 2.2.23, 3.1.21, and 3.2.6, Rack::Static#applicable_rules evaluates several header_rules types against the raw URL-encoded PATH_INFO, while the underlying file-serving path is decoded before the file is served. As a result, a request for a URL-encoded variant of a static path can serve the same file without the headers that header_rules were intended to apply. In deployments that rely on Rack::Static to attach security-relevant response headers to static content, this can allow an attacker to bypass those headers by requesting an encoded form of the path. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

Publish Date: 2026-04-02

URL: CVE-2026-34786

CVSS 3 Score Details (5.3)

Base Score Metrics:

• Exploitability Metrics:
  • Attack Vector: Network
  • Attack Complexity: Low
  • Privileges Required: None
  • User Interaction: None
  • Scope: Unchanged
• Impact Metrics:
  • Confidentiality Impact: None
  • Integrity Impact: Low
  • Availability Impact: None

Suggested Fix

Type: Upgrade version

Origin: https://github.com/advisories/GHSA-q4qf-9j86-f5mh

Release Date: 2026-04-02

Fix Resolution: rack - 3.1.21,rack - 3.2.6,rack - 2.2.23