{"id":"CVE-2026-54905","summary":"concurrent-ruby:  `ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity","details":"concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::ReentrantReadWriteLock can incorrectly grant a write lock after one thread acquires the read lock 32,768 times. The lock stores a thread's local read and write hold counts in one integer. The low 15 bits are used for the read hold count, and bit 15 is used as WRITE_LOCK_HELD. After 32,768 reentrant read acquisitions, the local read count crosses into the write-lock bit. try_write_lock then treats the thread as already holding a write lock and returns true without setting the global RUNNING_WRITER bit. This breaks the core mutual-exclusion guarantee: the caller is told it has a write lock, but other threads can still hold or acquire read locks at the same time. This vulnerability is fixed in 1.3.7.","aliases":["GHSA-wv3x-4vxv-whpp"],"modified":"2026-06-28T04:04:20.656291352Z","published":"2026-06-24T15:42:44.257Z","related":["CGA-7c4p-x579-jg35"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-128"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54905.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54905.json"},{"type":"ADVISORY","url":"https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54905"}],"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"},{"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/osv-test-cve-osv-conversion/osv-output/CVE-2026-54905.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N"}]}