Medium
ruby-concurrent — security advisory
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.
- Products
- ruby-concurrent
- Affected versions
- 1.0.0-1, 1.0.5-1, 1.0.5-3, 1.0.5-4, 1.1.6+dfsg-2, 1.1.6+dfsg-3, 1.1.6+dfsg-3build1, 1.1.6+dfsg-4, 1.1.6+dfsg-5build2, 1.1.6+dfsg-5build3, 1.2.3-2build1, 1.3.4-1, 1.3.6-1, 1.3.7-4, 1.3.8-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-54905
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 03:08 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-54905
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: Not specified
ruby-concurrent
Fixed versions: Not specified
Complete source record
{
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"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-54905",
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"summary": "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.",
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"modified": "2026-10-17T13:00:26.034613719Z",
"provider": "osv",
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}