CVE-2026-54906

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.2%, top 94% 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
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 0%CVSS: 9.8Exploit: 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::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.

CVSS v3
9.8
EG Score
9.8(medium)
EPSS
5.6%
KEV
Not listed

Published

June 19, 2026

Last Modified

June 26, 2026

Advisory Details (1)

Auto-updated Jul 12, 2026
🔬 Proof of concept available. Patch available. Sources: github.
github Patch Available🟡 PoC Available

ReadWriteLock allows wrong-thread write release and stray read-release counter corruption · Advisory · ruby-concurrency/concurrent-ruby · GitHub

https://github.com/ruby-concurrency/concurrent-ruby/security/advisories/GHSA-6wx8-w4f5-wwcr

Vendor Advisories for CVE-2026-54906(2)

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

Affected Packages

(1 across 1 ecosystem)
RubyGems(1)
PackageVulnerable rangeFixed inDependents
concurrent-ruby0.0.1 ... 1.3.6 (77 versions)1.3.7—

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 14× in last 7d / 134× 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.

Showing the most recent 100 of 135 total refreshes for this CVE.

  1. 2026-07-22 14:08 UTCEPSS rescore
  2. 2026-07-21 15:25 UTCEPSS rescore
  3. 2026-07-20 17:08 UTCEPSS rescore
  4. 2026-07-19 14:31 UTCEPSS rescore
  5. 2026-07-19 14:31 UTCEPSS rescore
  6. 2026-07-18 10:04 UTCEPSS rescore
  7. 2026-07-17 04:58 UTCVendor advisory
  8. 2026-07-17 00:50 UTCVendor advisory
  9. 2026-07-16 20:36 UTCVendor advisory
  10. 2026-07-16 17:03 UTCEPSS rescore
  11. 2026-07-16 11:22 UTCVendor advisory
  12. 2026-07-16 07:17 UTCVendor advisory
  13. 2026-07-16 02:12 UTCVendor advisory
  14. 2026-07-15 22:17 UTCVendor advisory
  15. 2026-07-15 18:22 UTCVendor advisory
  16. 2026-07-15 16:57 UTCEPSS rescore
  17. 2026-07-15 16:57 UTCEPSS rescore
  18. 2026-07-15 14:26 UTCVendor advisory
  19. 2026-07-15 10:29 UTCVendor advisory
  20. 2026-07-15 06:23 UTCVendor advisory
  21. 2026-07-15 02:00 UTCEPSS rescore
  22. 2026-07-15 02:00 UTCEPSS rescore
  23. 2026-07-15 00:52 UTCVendor advisory
  24. 2026-07-14 20:43 UTCVendor advisory
  25. 2026-07-14 16:43 UTCVendor advisory
Show 75 more
  1. 2026-07-14 12:49 UTCVendor advisory
  2. 2026-07-14 08:54 UTCVendor advisory
  3. 2026-07-14 04:55 UTCVendor advisory
  4. 2026-07-14 01:01 UTCVendor advisory
  5. 2026-07-13 22:31 UTCEPSS rescore
  6. 2026-07-13 06:13 UTCEPSS rescore
  7. 2026-07-13 06:13 UTCEPSS rescore
  8. 2026-07-13 05:27 UTCVendor advisory
  9. 2026-07-13 01:23 UTCVendor advisory
  10. 2026-07-12 21:28 UTCVendor advisory
  11. 2026-07-12 17:17 UTCVendor advisory
  12. 2026-07-12 13:21 UTCVendor advisory
  13. 2026-07-12 09:18 UTCVendor advisory
  14. 2026-07-12 05:46 UTCEPSS rescore
  15. 2026-07-12 05:23 UTCVendor advisory
  16. 2026-07-12 01:28 UTCVendor advisory
  17. 2026-07-11 21:33 UTCVendor advisory
  18. 2026-07-11 17:39 UTCVendor advisory
  19. 2026-07-11 13:44 UTCVendor advisory
  20. 2026-07-11 09:49 UTCVendor advisory
  21. 2026-07-11 08:27 UTCEPSS rescore
  22. 2026-07-11 08:27 UTCEPSS rescore
  23. 2026-07-11 05:54 UTCVendor advisory
  24. 2026-07-11 01:59 UTCVendor advisory
  25. 2026-07-10 21:46 UTCVendor advisory
  26. 2026-07-10 17:49 UTCVendor advisory
  27. 2026-07-10 13:55 UTCVendor advisory
  28. 2026-07-10 09:53 UTCVendor advisory
  29. 2026-07-10 05:39 UTCVendor advisory
  30. 2026-07-10 01:44 UTCVendor advisory
  31. 2026-07-09 21:48 UTCVendor advisory
  32. 2026-07-09 19:10 UTCEPSS rescore
  33. 2026-07-09 19:10 UTCEPSS rescore
  34. 2026-07-09 17:47 UTCVendor advisory
  35. 2026-07-09 13:51 UTCVendor advisory
  36. 2026-07-09 09:55 UTCVendor advisory
  37. 2026-07-09 06:01 UTCVendor advisory
  38. 2026-07-09 02:04 UTCVendor advisory
  39. 2026-07-08 22:08 UTCVendor advisory
  40. 2026-07-08 18:09 UTCVendor advisory
  41. 2026-07-08 15:16 UTCEPSS rescore
  42. 2026-07-08 15:16 UTCEPSS rescore
  43. 2026-07-08 14:15 UTCVendor advisory
  44. 2026-07-08 10:12 UTCVendor advisory
  45. 2026-07-08 06:17 UTCVendor advisory
  46. 2026-07-08 02:22 UTCVendor advisory
  47. 2026-07-07 22:28 UTCVendor advisory
  48. 2026-07-07 18:33 UTCVendor advisory
  49. 2026-07-07 13:46 UTCEPSS rescore
  50. 2026-07-07 13:46 UTCEPSS rescore
  51. 2026-07-07 12:30 UTCVendor advisory
  52. 2026-07-07 08:31 UTCVendor advisory
  53. 2026-07-07 04:31 UTCVendor advisory
  54. 2026-07-07 00:33 UTCVendor advisory
  55. 2026-07-06 20:38 UTCVendor advisory
  56. 2026-07-06 16:27 UTCEPSS rescore
  57. 2026-07-06 16:27 UTCEPSS rescore
  58. 2026-07-06 15:30 UTCVendor advisory
  59. 2026-07-06 11:28 UTCVendor advisory
  60. 2026-07-06 07:18 UTCVendor advisory
  61. 2026-07-06 03:18 UTCVendor advisory
  62. 2026-07-06 02:23 UTCEPSS rescore
  63. 2026-07-06 02:23 UTCEPSS rescore
  64. 2026-07-05 23:13 UTCVendor advisory
  65. 2026-07-05 19:18 UTCVendor advisory
  66. 2026-07-05 15:23 UTCVendor advisory
  67. 2026-07-05 11:26 UTCVendor advisory
  68. 2026-07-05 07:32 UTCVendor advisory
  69. 2026-07-05 03:35 UTCVendor advisory
  70. 2026-07-05 02:31 UTCEPSS rescore
  71. 2026-07-05 02:30 UTCEPSS rescore
  72. 2026-07-04 23:39 UTCVendor advisory
  73. 2026-07-04 19:45 UTCVendor advisory
  74. 2026-07-04 15:50 UTCVendor advisory
  75. 2026-07-04 11:47 UTCVendor advisory

Frequently asked(5)

What is CVE-2026-54906?
CVE-2026-54906 is a critical vulnerability published on June 19, 2026. concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::ReadWriteLock#releasewritelock 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…
When was CVE-2026-54906 disclosed?
CVE-2026-54906 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-2026-54906 actively exploited?
CVE-2026-54906 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 5.6% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-54906?
CVE-2026-54906 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2026-54906?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-54906, 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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