{"id":"AZL-91290","summary":"CVE-2026-54905 affecting package rubygem-concurrent-ruby for versions less than 1.3.7-1","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.","modified":"2026-08-28T17:47:39.196696392Z","published":"2026-06-24T17:17:29Z","upstream":["CVE-2026-54905"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54905"}],"affected":[{"package":{"name":"rubygem-concurrent-ruby","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/rubygem-concurrent-ruby"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.3.7-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-91290.json"}}],"schema_version":"1.9.0"}