CVE-2026-54904

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.

• CWE-835

• https://github.com/ruby-concurrency/concurrent-ruby/commit/6e37e0644b83b182971dc540d2e4bee38df61386
• https://github.com/ruby-concurrency/concurrent-ruby/releases/tag/v1.3.7
• https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-h8w8-99g7-qmvjExploit, Third Party Advisory
• https://github.com/rubysec/ruby-advisory-db/blob/master/gems/concurrent-ruby/CVE-2026-54904.yml
• https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-h8w8-99g7-qmvjExploit, Third Party Advisory

Published

Jun 24, 2026

Last Modified

Aug 5, 2026

Status

Modified

• How Strix found a critical auth bypass in etcdStrix autonomously discovered a critical authentication bypass in etcd, later designated CVE-2026-33413.
• Autonomous PentestingAI agents that find and validate exploitable vulnerabilities like this one across your applications.
• PR ReviewsPentest every pull request so vulnerable code is caught before it ships to production.
• AI Penetration TestingHow AI-driven penetration testing continuously covers your attack surface.

• CVE-2026-54899Oj (Optimized JSON) is a JSON parser and Object marshaller p…6.3
• CVE-2026-5490DriveLock SQL Injection Privilege Escalation Vulnerability. …8.8
• CVE-2026-54900Oj (Optimized JSON) is a JSON parser and Object marshaller p…6.3
• CVE-2026-54901Oj (Optimized JSON) is a JSON parser and Object marshaller p…6.3
• CVE-2026-54902Oj (Optimized JSON) is a JSON parser and Object marshaller p…6.3
• CVE-2026-54903Oj (Optimized JSON) is a JSON parser and Object marshaller p…6.3
• CVE-2026-54905concurrent-ruby is a modern concurrency tools for Ruby. Prio…5.5
• CVE-2026-54906concurrent-ruby is a modern concurrency tools for Ruby. Prio…9.8
• CVE-2026-54907Caddy Proxy Manager is a web interface for managing Caddy Se…5.3
• CVE-2026-54908Pion DTLS is a Go implementation of Datagram Transport Layer…6.3
• CVE-2026-54909pion/stun is a Go implementation of STUN. Prior to 3.1.3, XO…5.3
• CVE-2026-5491DriveLock Directory Traversal Information Disclosure Vulnera…7.5