CVE-2026-54905

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...

CVE-2026-54905

CVE-2026-54905 affects the concurrent-ruby library, specifically Concurrent::ReentrantReadWriteLock. Before version 1.3.7, after a thread acquires the read lock 32,768 times, the local read count overflows into the WRITE_LOCK_HELD bit, causing try_write_lock to treat the thread as if it holds a w...

Concurrent Ruby: `ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity

Summary 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 WRITELOCKHELD...