Vulnerability in Ruby-Concurrency Concurrent-Ruby
CVE-2026-54906
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
EPSS: 0.003 (15.0th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 15th percentile — 15.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Ruby-Concurrency Concurrent-Ruby — versions < 1.3.7
- Rubyconcurrency Concurrent Ruby
Weakness classification (CWE)
References
- github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-… (Third Party Advisory)
Frequently asked questions
- What is CVE-2026-54906?
- CVE-2026-54906 is a critical-severity vulnerability in Ruby-Concurrency Concurrent-Ruby, classified under CWE-414. CVSS score: 9.8/10. Published 2026-06-24.
- How severe is CVE-2026-54906?
- Critical severity. CVSS v3 base score is 9.8 out of 10.