CVE-2026-54905 (Medium) detected in concurrent-ruby-1.3.6.gem

Nobody has claimed this yet.

## CVE-2026-54905 - Medium Severity Vulnerability
Vulnerable Library - concurrent-ruby-1.3.6.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-1.3.6.gem

Path to dependency file: /Gemfile.lock

Path to vulnerable library: /vendor/cache/concurrent-ruby-1.3.6.gem

Dependency Hierarchy:
- activesupport-7.1.6.gem (Root Library)
- :x: **concurrent-ruby-1.3.6.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::ReentrantReadWriteLock can incorrectly grant a write lock after one thread acquires the read lock 32,768 times. The lock stores a thread's local read and write hold counts in one integer. The low 15 bits are used for the read hold count, and bit 15 is used as WRITE_LOCK_HELD. After 32,768 reentrant read acquisitions, the local read count crosses into the write-lock bit. try_write_lock then treats the thread as already holding a write lock and returns true without setting the global RUNNING_WRITER bit. This breaks the core mutual-exclusion guarantee: the caller is told it has a write lock, but other threads can still hold or acquire read locks at the same time. This vulnerability is fixed in 1.3.7.

Publish Date: 2026-06-24

URL: CVE-2026-54905

CVSS 3 Score Details (5.3)

Base Score Metrics:
- Exploitability Metrics:
- Attack Vector: Local
- Attack Complexity: Low
- Privileges Required: Low
- User Interaction: None
- Scope: Unchanged
- Impact Metrics:
- Confidentiality Impact: Low
- Integrity Impact: Low
- Availability Impact: Low

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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Start with Gemfile.lock and the vendored dependency at vendor/cache/concurrent-ruby-1.3.6.gem; verify how the current concurrent-ruby version is selected and stored. Update the dependency to concurrent-ruby 1.3.7, then confirm the lockfile and vendor cache no longer use 1.3.6 and run the project's test suite.

Written by the indexing model from the issue text.