{"id":"CVE-2026-54905","aliases":["GHSA-wv3x-4vxv-whpp"],"url":"https://o3.security/vulnerability/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.","published":"2026-06-24T15:42:44.257Z","modified":"2026-08-12T03:51:20.521628085Z","cvss":null,"epss":{"score":0.00153,"percentile":0.04742,"asOf":"2026-09-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"concurrent-ruby","fixedVersion":"1.3.7"}],"fix":null,"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:20.521628085Z"}}