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
Trending — 3 sources updated this week
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 3, 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 88× in last 7d / 113× 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 113 total refreshes for this CVE.

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

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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