{"id":"CVE-2026-54904","summary":"concurrent-ruby:  `AtomicReference#update` livelocks when the stored value is `Float::NAN`","details":"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.","aliases":["GHSA-h8w8-99g7-qmvj"],"modified":"2026-07-08T08:13:42.561920691Z","published":"2026-06-24T15:44:21.992Z","related":["CGA-cc84-6xxr-92xm"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-835"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54904.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54904.json"},{"type":"ADVISORY","url":"https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-h8w8-99g7-qmvj"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54904"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/ruby-concurrency/concurrent-ruby","events":[{"introduced":"0"},{"fixed":"4c8fc28ab6bb9bd8258a4c0c2fa6d35ebe77b3cb"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"1.3.7"}],"source":["AFFECTED_FIELD","CPE_RANGE"],"cpe":"cpe:2.3:a:rubyconcurrency:concurrent_ruby:*:*:*:*:*:ruby:*:*"}}],"versions":["v1.3.6","v1.3.5","edge-v0.7.2","v1.3.4","v1.3.3","v1.3.2","edge-v0.7.1","v1.3.1","v1.3.1.pre","v1.3.0","v1.2.3","v1.2.2","v1.2.1","edge-v0.7.0","v1.2.0","v1.1.9","v1.1.8","v1.1.7","v1.1.6","edge-v0.6.0","v1.1.6.pre1","edge-v0.6.0.pre1","v1.1.5","edge-v0.5.0","v1.1.4","v1.1.3","v1.1.2","v1.1.1","edge-v0.4.1","v1.1.0","edge-v0.4.0","v1.1.0.pre2","edge-v0.4.0.pre2","v1.1.0.pre1","edge-v0.4.0.pre1","v1.0.3","edge-v0.2.3","v1.0.5","edge-v0.3.1","v1.0.4","edge-v0.3.0","v1.0.3.pre3","v1.0.3.pre2","v1.0.3.pre1","v1.0.2","v1.0.1","v1.0.0","v1.0.0.pre5","v0.9.1","v1.0.0.pre4","1.0.0.pre3","1.0.0.pre2","v1.0.0.pre1","v0.9.0","v0.9.0.pre3","v0.9.0.pre2","v0.9.0.pre1","v0.8.0","v0.7.2","v0.7.0.1","v0.7.0","v0.7.0.rc3","v0.7.0.rc2","v0.7.0.rc1","v0.6.1","v0.6.0","v0.6.0.pre.2","v0.6.0.pre.1","v0.4.0","v0.3.2","v0.3.1","v0.3.1.pre.2","v0.3.1.pre.1","v0.3.0","v0.3.0.pre.3","v0.3.0.pre.2","0.3.0.pre.1","v0.2.2","v0.0.2","v0.2.1","v0.2.0","v0.1.1.pre.5","v0.1.1.pre.4","v0.1.1.pre.2","v0.1.0","v0.0.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54904.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}