CVE-2026-54904
CVE-2026-54904 updated by NVD
Summary
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.
Affected packages
| Ecosystem | Package | Affected versions | Fixed versions |
|---|---|---|---|
| RubyGems | concurrent-ruby | — | 1.3.7 |
Remediation: Upgrade to 1.3.7 or later.
References
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EPSS scores provided by the FIRST.org Exploit Prediction Scoring System.