Hacktoberfest 2026: the issues maintainers tagged for October, open and beginner-friendly. Browse Hacktoberfest issues

CVE-2026-34831 (Medium) detected in rack-3.1.16.gem

Open
  • Is something wrong?
#283 0 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
58/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Quiet
Tech stack
ruby
Domain
security

Research direction

Start with /Gemfile.lock and the vendored dependency at /vendor/cache/rack-3.1.16.gem, then inspect the dependency hierarchy showing rack is pulled through rubocop-rails. Update the resolved Rack version to one of the listed fixed releases and verify that the lockfile and vendored package no longer contain 3.1.16.

Written by the indexing model from the issue text.

Description

Mend: dependency security vulnerability

CVE-2026-34831 - Medium Severity Vulnerability

Vulnerable Library - rack-3.1.16.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-3.1.16.gem

Path to dependency file: /Gemfile.lock

Path to vulnerable library: /vendor/cache/rack-3.1.16.gem

Dependency Hierarchy:

  • manageiq-style-1.3.3.gem (Root Library)
    • rubocop-rails-2.32.0.gem
      • ❌ rack-3.1.16.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::Files#fail sets the Content-Length response header using String#size instead of String#bytesize. When the response body contains multibyte UTF-8 characters, the declared Content-Length is smaller than the number of bytes actually sent on the wire. Because Rack::Files reflects the requested path in 404 responses, an attacker can trigger this mismatch by requesting a non-existent path containing percent-encoded UTF-8 characters. This results in incorrect HTTP response framing and may cause response desynchronization in deployments that rely on the incorrect Content-Length value. This issue has been patched in versions 2.2.23, 3.1.21, and 3.2.6.

Publish Date: 2026-04-02

URL: CVE-2026-34831

CVSS 3 Score Details (4.8)

Base Score Metrics:

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

For more information on CVSS3 Scores, click here.

Suggested Fix

Type: Upgrade version

Origin: https://github.com/advisories/GHSA-q2ww-5357-x388

Release Date: 2026-04-02

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

Step up your Open Source Security Game with Mend here

Dominant language
Ruby
Stars
30
Forks
27
No merged PRs in 30d

Getting set up

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from ManageIQ/linux_admin

All issues in ManageIQ/linux_admin

Similar issues

More Ruby issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.