CVE-2026-54905

MEDIUMNVD 5.55.5—
EchelonGraph scoreMEDIUM confidence

This medium-severity CVE scores 5.5 under NVD CVSS v3. EPSS exploit probability: 0.1%, top 99% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
5.5
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS: 0%CVSS: 5.5Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
5.5
EG Score
5.5(medium)
EPSS
1.3%
KEV
Not listed

Published

June 19, 2026

Last Modified

June 26, 2026

Advisory Details (1)

Auto-updated Jun 26, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

`ReentrantReadWriteLock` read-count overflow grants a write lock without exclusivity · Advisory · ruby-concurrency/concurrent-ruby · GitHub

https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-wv3x-4vxv-whpp

Vendor Advisories for CVE-2026-54905(2)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Data Freshness Timeline

(refreshed 21× in last 7d / 34× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-06 17:08 UTCEG score recompute
  2. 2026-07-06 17:08 UTCVendor advisory
  3. 2026-07-06 02:23 UTCEPSS rescore
  4. 2026-07-06 02:23 UTCEPSS rescore
  5. 2026-07-05 17:52 UTCEG score recompute
  6. 2026-07-05 17:52 UTCVendor advisory
  7. 2026-07-05 02:31 UTCEPSS rescore
  8. 2026-07-05 02:30 UTCEPSS rescore
  9. 2026-07-04 18:40 UTCEG score recompute
  10. 2026-07-04 18:40 UTCVendor advisory
  11. 2026-07-04 06:31 UTCEPSS rescore
  12. 2026-07-04 06:31 UTCEPSS rescore
  13. 2026-07-03 19:30 UTCEG score recompute
  14. 2026-07-03 19:30 UTCVendor advisory
  15. 2026-07-02 20:21 UTCEG score recompute
  16. 2026-07-02 20:21 UTCVendor advisory
  17. 2026-07-01 21:12 UTCEG score recompute
  18. 2026-07-01 21:12 UTCVendor advisory
  19. 2026-07-01 15:07 UTCEPSS rescore
  20. 2026-06-30 23:22 UTCEPSS rescore
  21. 2026-06-30 22:03 UTCEG score recompute
  22. 2026-06-29 22:53 UTCEG score recompute
  23. 2026-06-29 14:06 UTCEPSS rescore
  24. 2026-06-29 14:06 UTCEPSS rescore
  25. 2026-06-28 23:44 UTCEG score recompute
Show 9 more
  1. 2026-06-28 14:07 UTCEPSS rescore
  2. 2026-06-28 04:56 UTCEPSS rescore
  3. 2026-06-28 04:56 UTCEPSS rescore
  4. 2026-06-28 00:35 UTCEG score recompute▲ 3.50
  5. 2026-06-26 21:42 UTCNVD updateCVSS v3 → 5.5 · severity → MEDIUM
  6. 2026-06-25 13:49 UTCEPSS rescore
  7. 2026-06-24 18:32 UTCEG score recompute▲ 2.00
  8. 2026-06-24 18:03 UTCNVD updateCVSS v3 → 2 · CVSS v4 → 2
  9. 2026-06-19 21:24 UTCEG score recompute

Frequently asked(5)

What is CVE-2026-54905?
CVE-2026-54905 is a medium vulnerability published on June 19, 2026. 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…
When was CVE-2026-54905 disclosed?
CVE-2026-54905 was first published in the National Vulnerability Database on June 19, 2026, with the most recent update on June 26, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-54905 actively exploited?
CVE-2026-54905 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 1.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-54905?
CVE-2026-54905 has a CVSS v3 base score of 5.5 (NVD).
How do I remediate CVE-2026-54905?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54905, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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