CVE-2026-54906

CRITICALNVD 9.89.8
EchelonGraph scoreMEDIUM confidence

“—” beside the score: it is equal to NVD's CVSS score.

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 0.2% (5th percentile of EPSS-scored CVEs). No GitHub Security Advisory CVSS is on record for this CVE.

Triggered by: Headline CVSS from NVD CVSS v3
Sources: EPSS, NVD CVSS v3
Elevated

Also known asEUVD-2026-38811 (ENISA EUVD) · GHSA-6wx8-w4f5-wwcr (GitHub Security Advisories)Source: ENISA EUVD

9.8EG
EchelonGraph verdictPlan a fixRemediate within your standard update timelines (the SSVC decision on this page).
  • CISA's Vulnrichment rates exploitation as PoC; EchelonGraph holds no exploit-code reference for it
CISA-KEV: Not listedEPSS PROB: 0.2%CVSS: 9.8Exploit: No code on recordExposed services: Not assessed

A fix is available — apply it.

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
9.8CRITICALmedium confidence
EG Risk
60
EG Risk 60/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity98% × 45%
Impact severity (EG Severity): CVSS 9.8 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation40% × 40%
EchelonGraph's fixed weight for EG-KEV Tier 3 (Elevated): a constant, not a probability.
Automatability0% × 15%
CISA's SSVC Automatable value: no (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).
Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: A fix is available. Apply it within your standard update timelines.
EPSS PROB
0.2%
EPSS %ILE
5th
KEV
Not listed

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.8): severity, escalated by confirmed exploitation. This CVE's 9.8 is its impact severity (EG Severity), not escalated.

EG Severity
9.8 CRITICALCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-12). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).

A fix is available. Apply it within your standard update timelines.

Exploitation public PoC (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.

The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

Published

June 19, 2026

Last Modified

October 25, 2026

Advisory Details (1)

Auto-updated Nov 9, 2026
🔬 Proof of concept available. Patch available. Sources: github.
GitHub advisoryMentions a patch (unverified)🟡 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.

Patch Availability(1)

Vendor / EcosystemFix (by version range) / PatchReleasedSource
rubygemsconcurrent-ruby @ 1.3.7 (fixes < 1.3.7)—ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(5 across 5 ecosystems)
Debian:11(1)
PackageVulnerable rangeFix by version rangeDependents
ruby-concurrent1.1.6+dfsg-3 ... 1.3.8-1 (16 versions)
  • every version on: no fix on record
—
Debian:12(1)
PackageVulnerable rangeFix by version rangeDependents
ruby-concurrent1.1.6+dfsg-5 ... 1.3.8-1 (14 versions)
  • every version on: no fix on record
—
Debian:13(1)
PackageVulnerable rangeFix by version rangeDependents
ruby-concurrent1.3.5-1 ... 1.3.8-1 (7 versions)
  • every version on: no fix on record
—
Debian:14(1)
PackageVulnerable rangeFix by version rangeDependents
ruby-concurrent1.3.5-1, 1.3.6-1
  • every version up to 1.3.7-1: fixed in 1.3.7-1
—
RubyGems(1)
PackageVulnerable rangeFix by version rangeDependents
concurrent-ruby0.0.1 ... 1.3.6 (77 versions)
  • every version up to 1.3.7: fixed in 1.3.7
—

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 19× in last 7d / 65× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed its CVE.org record (CNA or CISA ADP). An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). "EchelonGraph re-scored" is our own recompute of this CVE's score, not an update from a source, and is not counted in the refreshes above. Most recent first.

Showing the most recent 100 of 464 rows on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 364 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-13 16:53 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  2. 2026-11-13 11:31 UTCEchelonGraph re-scored
  3. 2026-11-13 11:31 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  4. 2026-11-12 16:34 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  5. 2026-11-12 12:56 UTCEchelonGraph re-scored
  6. 2026-11-12 12:56 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  7. 2026-11-11 16:40 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  8. 2026-11-11 14:22 UTCEchelonGraph re-scored
  9. 2026-11-11 14:22 UTCVendor advisory
  10. 2026-11-11 14:22 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  11. 2026-11-10 16:44 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  12. 2026-11-10 15:48 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  13. 2026-11-09 17:13 UTCEchelonGraph re-scored
  14. 2026-11-09 17:13 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  15. 2026-11-09 16:35 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  16. 2026-11-08 18:39 UTCEchelonGraph re-scored
  17. 2026-11-08 18:39 UTCVendor advisory
  18. 2026-11-08 18:39 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  19. 2026-11-08 16:40 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  20. 2026-11-07 20:05 UTCEchelonGraph re-scored
  21. 2026-11-07 20:05 UTCVendor advisory
  22. 2026-11-07 20:05 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  23. 2026-11-07 16:39 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  24. 2026-11-06 21:29 UTCEchelonGraph re-scored
  25. 2026-11-06 21:29 UTCVendor advisory
Show 75 more
  1. 2026-11-06 21:29 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  2. 2026-11-06 16:38 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  3. 2026-11-06 12:25 UTCOSV refresh
  4. 2026-11-05 22:54 UTCEchelonGraph re-scored
  5. 2026-11-05 22:54 UTCVendor advisory
  6. 2026-11-05 22:54 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  7. 2026-11-05 16:38 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  8. 2026-11-05 00:20 UTCEchelonGraph re-scored
  9. 2026-11-05 00:20 UTCVendor advisory
  10. 2026-11-05 00:20 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  11. 2026-11-04 16:35 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  12. 2026-11-04 01:46 UTCEchelonGraph re-scored
  13. 2026-11-04 01:46 UTCVendor advisory
  14. 2026-11-04 01:46 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  15. 2026-11-03 16:48 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  16. 2026-11-03 03:12 UTCEchelonGraph re-scored
  17. 2026-11-03 03:12 UTCVendor advisory
  18. 2026-11-03 03:12 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  19. 2026-11-02 16:45 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  20. 2026-11-02 04:36 UTCEchelonGraph re-scored
  21. 2026-11-02 04:36 UTCVendor advisory
  22. 2026-11-02 04:36 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  23. 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  24. 2026-11-01 07:44 UTCGHSA enrichmentGHSA-6wx8-w4f5-wwcr · GitHub severity LOW
  25. 2026-11-01 06:02 UTCEchelonGraph re-scored
  26. 2026-11-01 06:02 UTCVendor advisory
  27. 2026-10-31 16:33 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  28. 2026-10-31 07:28 UTCEchelonGraph re-scored
  29. 2026-10-31 07:28 UTCVendor advisory
  30. 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  31. 2026-10-30 08:53 UTCEchelonGraph re-scored
  32. 2026-10-30 08:53 UTCVendor advisory
  33. 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  34. 2026-10-29 10:19 UTCEchelonGraph re-scored
  35. 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  36. 2026-10-28 11:45 UTCEchelonGraph re-scored
  37. 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  38. 2026-10-27 00:40 UTCEchelonGraph re-scored
  39. 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  40. 2026-10-25 22:26 UTCEchelonGraph re-scored
  41. 2026-10-25 22:26 UTCVendor advisory
  42. 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.2% · 5th percentile
  43. 2026-10-25 14:19 UTCEchelonGraph re-scored
  44. 2026-10-25 13:10 UTCEchelonGraph re-scored
  45. 2026-10-25 13:10 UTCVendor advisory
  46. 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  47. 2026-10-24 14:36 UTCEchelonGraph re-scored
  48. 2026-10-24 14:36 UTCVendor advisory
  49. 2026-10-23 16:32 UTCEPSS rescoreEPSS 0.2% · 4th percentile
  50. 2026-10-22 17:19 UTCEchelonGraph re-scored
  51. 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  52. 2026-10-21 18:31 UTCEchelonGraph re-scored
  53. 2026-10-21 18:31 UTCVendor advisory
  54. 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  55. 2026-10-20 19:57 UTCEchelonGraph re-scored
  56. 2026-10-20 19:57 UTCVendor advisory
  57. 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  58. 2026-10-19 21:22 UTCEchelonGraph re-scored
  59. 2026-10-19 21:22 UTCVendor advisory
  60. 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  61. 2026-10-18 20:49 UTCEchelonGraph re-scored
  62. 2026-10-18 20:49 UTCVendor advisory
  63. 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  64. 2026-10-18 03:30 UTCEchelonGraph re-scored
  65. 2026-10-17 21:54 UTCEchelonGraph re-scored
  66. 2026-10-17 21:54 UTCVendor advisory
  67. 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  68. 2026-10-16 23:17 UTCEchelonGraph re-scored
  69. 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  70. 2026-10-15 20:34 UTCEchelonGraph re-scored
  71. 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  72. 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  73. 2026-10-14 14:27 UTCEchelonGraph re-scored
  74. 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 15th percentile
  75. 2026-10-13 14:09 UTCEchelonGraph re-scored

Related CVEs(same product + same CWE)

Same product

2 shown

Debian:11:ruby-concurrent

Frequently asked(5)

What is CVE-2026-54906?
CVE-2026-54906 is a critical-severity vulnerability; its CVE record was published on June 19, 2026. 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…
When was the CVE record for CVE-2026-54906 published?
The CVE record for CVE-2026-54906 was published on June 19, 2026. That is the record's publication date; the vulnerability itself may have been made public earlier. EchelonGraph's copy of the record carries a last-modified date of October 25, 2026; the record at its source may have been updated since.
Is CVE-2026-54906 actively exploited?
CVE-2026-54906 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.2% probability of exploitation in the next 30 days (5th percentile of EPSS-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?
A fix for CVE-2026-54906 is available: update to the fixed version the vendor names in its advisory. The vendor advisories EchelonGraph has for CVE-2026-54906 are linked in the Vendor Advisories panel on this page.

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