CVE-2026-54904

Description

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.

Weakness classification

• security-advisories@github.com: CWE-835

Primary references

• security-advisories@github.com
• security-advisories@github.com
• security-advisories@github.com — Exploit, Third Party Advisory
• security-advisories@github.com
• 134c704f-9b21-4f2e-91b3-4a467353bcc0 — Exploit, Third Party Advisory