CVE-2026-34827 (High) detected in rack-3.2.5.gem

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Assessment

Difficulty
1/5
Estimated time
Under an hour
Newbie friendliness
72/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
ruby
Domain
security

Research direction

Start with /Gemfile.lock and the cached dependency at /vendor/cache/rack-3.2.5.gem. Upgrade Rack to 3.2.6 or later, refresh the lockfile and vendored gem, then verify that the vulnerable 3.2.5 dependency is no longer present.

Written by the indexing model from the issue text.

Description

Mend: dependency security vulnerability

CVE-2026-34827 - High Severity Vulnerability

Vulnerable Library - rack-3.2.5.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-3.2.5.gem

Path to dependency file: /Gemfile.lock

Path to vulnerable library: /vendor/cache/rack-3.2.5.gem

Dependency Hierarchy:

  • manageiq-style-1.6.0.gem (Root Library)
    • ❌ rack-3.2.5.gem (Vulnerable Library)

Found in base branch: master

Vulnerability Details

Rack is a modular Ruby web server interface. From versions 3.0.0.beta1 to before 3.1.21, and 3.2.0 to before 3.2.6, Rack::Multipart::Parser#handle_mime_head parses quoted multipart parameters such as Content-Disposition: form-data; name="..." using repeated String#index searches combined with String#slice! prefix deletion. For escape-heavy quoted values, this causes super-linear processing. An unauthenticated attacker can send a crafted multipart/form-data request containing many parts with long backslash-escaped parameter values to trigger excessive CPU usage during multipart parsing. This results in a denial of service condition in Rack applications that accept multipart form data. This issue has been patched in versions 3.1.21 and 3.2.6.

Publish Date: 2026-04-02

URL: CVE-2026-34827

CVSS 3 Score Details (7.5)

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: High

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: https://github.com/advisories/GHSA-v6x5-cg8r-vv6x

Release Date: 2026-04-02

Fix Resolution: rack - 3.2.6,rack - 3.1.21

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Dominant language
Ruby
Stars
2
Forks
22
No merged PRs in 30d

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First steps

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