# CVE-2026-54906

## Summary

- **CVE ID:** CVE-2026-54906
- **Severity:** LOW
- **CVSS Score:** 2.1 (CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N)
- **CWE:** CWE-667, CWE-414
- **Published:** Jun 24, 2026
- **Last Modified:** Jun 24, 2026

## Description

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.

## Affected Products

- ruby-concurrency — concurrent-ruby (< 1.3.7)

## References

- [CNA](https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.25%
- **EPSS Percentile:** 16.6

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-10._