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
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 9.8Exploit: None knownExposed: 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)
EG Risk
49(Track)
EG Risk 49/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation0% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
6%
KEV
Not listed

Published

June 19, 2026

Last Modified

June 26, 2026

Advisory Details (1)

Auto-updated Aug 22, 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

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFixed inDependents
ruby-concurrent1.1.6+dfsg-3 ... 1.3.8-1 (16 versions)——
Debian:12(1)
PackageVulnerable rangeFixed inDependents
ruby-concurrent1.1.6+dfsg-5 ... 1.3.8-1 (14 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
ruby-concurrent1.3.5-1 ... 1.3.8-1 (7 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
ruby-concurrent1.3.5-1, 1.3.6-11.3.7-1—
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 31× in last 7d / 162× 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 299 total refreshes for this CVE.

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

Related CVEs(same vendor + same CWE)

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 0% probability of exploitation in the next 30 days, which ranks it in the top 94.3% of all scored CVEs.
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.

Dependency Blast Radius

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