CVE-2026-34230 (Medium) detected in rack-2.2.9.gem

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
ruby
Domain
security

Research direction

Start with /Gemfile.lock and inspect the rack-2.2.9 dependency brought in through rack-test-2.1.0. Upgrade Rack to a fixed version listed in the issue, then verify that dependency resolution succeeds and the vulnerability is no longer reported.

Written by the indexing model from the issue text.

Description

Mend: dependency security vulnerability

CVE-2026-34230 - Medium Severity Vulnerability

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::Utils.select_best_encoding processes Accept-Encoding values with quadratic time complexity when the header contains many wildcard (*) entries. Because this method is used by Rack::Deflater to choose a response encoding, an unauthenticated attacker can send a single request with a crafted Accept-Encoding header and cause disproportionate CPU consumption on the compression middleware path. This results in a denial of service condition for applications using Rack::Deflater. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

Publish Date: 2026-04-02

URL: CVE-2026-34230

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: None
    • Availability Impact: Low

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: https://github.com/advisories/GHSA-v569-hp3g-36wr

Release Date: 2026-04-02

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

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Dominant language
Ruby
Stars
1
Forks
12
No merged PRs in 30d

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