CVE-2026-54905 concurrent-ruby: `ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity

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...

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...