Quick answers
- Is CVE-2026-54906 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-54906 being exploited in the wild.
- How severe is CVE-2026-54906?
- Medium severity, with a CVSS score of 4, published 24 June 2026.
- Which products and versions are affected?
- concurrent-ruby (RubyGems) < 1.3.7, ECOSYSTEM:introduced=0,fixed=1.3.7.
- Is there a fix for CVE-2026-54906?
- Yes. concurrent-ruby (RubyGems): upgrade to 1.3.7 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-54906 attacked?
- It is attacked with local access, in a software library.
- Am I affected by CVE-2026-54906?
- Check whether you run concurrent-ruby (RubyGems) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- concurrent-ruby (RubyGems): upgrade to 1.3.7 or later
bundle update concurrent-ruby
Technical details
A vulnerability exists in Concurrent::ReadWriteLock where the #release_write_lock method fails to verify if the calling thread is the actual owner of the lock. This allows an arbitrary thread to release a write lock held by another, potentially allowing a second writer to enter a critical section concurrently and causing data races. Additionally, #release_read_lock unconditionally decrements the internal counter even if no lock is held; calling this on a fresh lock results in a negative counter value, which causes subsequent read acquisitions to fail with a Concurrent::ResourceLimitError. These issues are addressed in version 1.3.7.
Affected products
- ruby-concurrency concurrent-ruby < 1.3.7
Identifiers
- CVE-2026-54906
- GHSA-6wx8-w4f5-wwcr
Timeline
- 2026-06-16: advisory: GitHub security advisory published
- 2026-06-24: disclosed: CVE published to NVD