concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::ReadWriteLock#release_write_lock does not verify that the calling thread acquired the write lock. Any thread with access to the lock object can release an active write lock held by another thread. A second writer can then enter its critical section while the first writer is still running. Concurrent::ReadWriteLock#release_read_lock also decrements the shared counter even when no read lock is held. Calling it on a fresh lock changes the counter from 0 to -1, after which normal read acquisition raises Concurrent::ResourceLimitError. This is a synchronization correctness issue in the public Concurrent::ReadWriteLock API. This vulnerability is fixed in 1.3.7.
Weakness
A product does not check to see if a lock is present before performing sensitive operations on a resource.
Affected Software
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Concurrent_ruby | Rubyconcurrency | * | 1.3.7 (excluding) |
| Ruby-concurrent | Ubuntu | questing | * |
| Ruby-concurrent | Ubuntu | upstream | * |