Quick answers
- Is CVE-2026-54904 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-54904 being exploited in the wild.
- How severe is CVE-2026-54904?
- High severity, with a CVSS score of 3.1, 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-2026-54904?
- 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-2026-54904 attacked?
- It is attacked over the network, in a software library.
- Am I affected by CVE-2026-54904?
- 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 livelock vulnerability exists in Concurrent::AtomicReference#update due to the interaction between Ruby's NaN semantics and the library's retry logic. The #update method retries until compare_and_set returns true; however, compare_and_set performs a numeric equality check (==) before the atomic swap. Because Float::NAN == Float::NAN is always false in Ruby, the check fails indefinitely when the reference contains a NaN value. An attacker who can influence numeric data stored in an AtomicReference can trigger this infinite loop, leading to CPU exhaustion and thread hangs. The issue is resolved in version 1.3.7.
Affected products
- ruby-concurrency concurrent-ruby < 1.3.7
Identifiers
- CVE-2026-54904
- GHSA-h8w8-99g7-qmvj
Timeline
- 2026-06-16: advisory: GitHub Security Advisory published
- 2026-06-24: disclosed: NVD publication date