CVE-2026-54904 (High) detected in concurrent-ruby-1.3.5.gem

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
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 /vendor/cache/concurrent-ruby-1.3.5.gem, then trace the dependency chain described in the issue. Update the vulnerable concurrent-ruby dependency to 1.3.7 and verify that the lockfile and cached dependency no longer reference 1.3.5 and that the vulnerability scan passes.

Written by the indexing model from the issue text.

Description

Mend: dependency security vulnerability

CVE-2026-54904 - High Severity Vulnerability

Vulnerable Library - concurrent-ruby-1.3.5.gem

Modern concurrency tools including agents, futures, promises, thread pools, actors, supervisors, and more. Inspired by Erlang, Clojure, Go, JavaScript, actors, and classic concurrency patterns.

Library home page: https://rubygems.org/gems/concurrent-ruby-1.3.5.gem

Path to dependency file: /Gemfile.lock

Path to vulnerable library: /vendor/cache/concurrent-ruby-1.3.5.gem

Dependency Hierarchy:

  • manageiq-style-1.5.9.gem (Root Library)
    • rubocop-rails-2.29.1.gem
      • activesupport-8.1.1.gem
        • ❌ concurrent-ruby-1.3.5.gem (Vulnerable Library)

Found in base branch: master

Vulnerability Details

concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::AtomicReference#update can enter a permanent busy retry loop when the current value is Float::NAN. The issue is caused by the interaction between AtomicReference#update, which retries until compare_and_set(old_value, new_value) succeeds; Numeric compare_and_set, which checks old == old_value before attempting the underlying atomic swap.; and Ruby NaN semantics, where Float::NAN == Float::NAN is always false. As a result, once an AtomicReference contains Float::NAN, calling #update repeatedly evaluates the caller's block and never returns. In services that store externally derived numeric values in an AtomicReference, this can cause CPU exhaustion or permanent request/job hangs. This vulnerability is fixed in 1.3.7.

Publish Date: 2026-06-24

URL: CVE-2026-54904

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

Release Date: 2026-06-19

Fix Resolution: https://github.com/ruby-concurrency/concurrent-ruby.git - v1.3.7

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Dominant language
Ruby
Stars
6
Forks
8
No merged PRs in 30d

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