CVE-2026-81666

MEDIUMPre-NVD 6.56.5—
EchelonGraph scoreHIGH confidence

Score 6.5 from GitHub Security Advisory published 2026-09-04. a secondary CVSS source baseline 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, secondary
Trending — 3 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

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

An integer overflow was found in Corosync's handling of membership commit token messages. The length-validation check for these messages can be bypassed on 32-bit systems due to an integer overflow in the calculation of the expected message length, allowing a crafted network packet to trigger an out-of-bounds memory access that crashes the Corosync daemon. This results in a denial of service for the affected cluster node. The overflow does not occur on 64-bit systems, where the length calculation is correctly performed in 64-bit arithmetic.

CVSS v3
6.5
EG Score
6.5(high)
EG Risk
29(Track)
EG Risk 29/100SSVC: 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
Severity65% × 45%
Exploitation0% × 40%
Automatability0% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
20%
KEV
Not listed

Published

September 4, 2026

Last Modified

September 8, 2026

Advisory Details (2)

Auto-updated Sep 4, 2026
Patch available. Sources: redhat.
redhat

2524923 – (CVE-2026-81666) CVE-2026-81666 corosync: corosync: integer overflow in check_memb_commit_token_sanity may bypass message length validation on 32-bit systems

https://bugzilla.redhat.com/show_bug.cgi?id=2524923
redhat Patch Available

CVE-2026-81666 - Red Hat Customer Portal

Affected: Red Hat Enterprise Linux 8, 9, and 10 ship primarily 64-bit architectures (x86_64, aarch64), so this specific overflow mechani

https://access.redhat.com/security/cve/CVE-2026-81666

Vendor Advisories for CVE-2026-81666(1)

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

Affected Packages

(3 across 3 ecosystems)
Debian:12(1)
PackageVulnerable rangeFixed inDependents
corosync3.1.10-1 ... 3.1.9-2 (12 versions)——
Debian:13(1)
PackageVulnerable rangeFixed inDependents
corosync3.1.10-1 ... 3.1.9-2+deb13u1 (6 versions)——
Debian:14(1)
PackageVulnerable rangeFixed inDependents
corosync3.1.10-1, 3.1.10-2, 3.1.10-3, 3.1.10-4, 3.1.9-2——

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 18× in last 7d / 50× 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. 2026-09-20 20:16 UTCEPSS rescore
  2. 2026-09-20 19:39 UTCGHSA enrichment
  3. 2026-09-19 21:32 UTCEG score recompute
  4. 2026-09-19 21:32 UTCGHSA enrichment
  5. 2026-09-18 23:24 UTCEG score recompute
  6. 2026-09-18 23:24 UTCGHSA enrichment
  7. 2026-09-18 19:28 UTCEPSS rescore
  8. 2026-09-18 01:17 UTCEG score recompute
  9. 2026-09-18 01:17 UTCGHSA enrichment
  10. 2026-09-17 03:10 UTCEG score recompute
  11. 2026-09-17 03:10 UTCGHSA enrichment
  12. 2026-09-16 14:08 UTCEPSS rescore
  13. 2026-09-16 05:15 UTCEPSS rescore
  14. 2026-09-16 05:02 UTCGHSA enrichment
  15. 2026-09-15 06:55 UTCEG score recompute
  16. 2026-09-15 06:55 UTCGHSA enrichment
  17. 2026-09-15 03:12 UTCEPSS rescore
  18. 2026-09-15 03:12 UTCEPSS rescore
  19. 2026-09-14 08:47 UTCEG score recompute
  20. 2026-09-14 08:47 UTCGHSA enrichment
  21. 2026-09-13 10:40 UTCEG score recompute
  22. 2026-09-13 10:40 UTCGHSA enrichment
  23. 2026-09-12 12:33 UTCEG score recompute
  24. 2026-09-12 12:33 UTCGHSA enrichment
  25. 2026-09-11 14:53 UTCEPSS rescore
Show 25 more
  1. 2026-09-11 14:53 UTCEPSS rescore
  2. 2026-09-11 14:25 UTCEG score recompute
  3. 2026-09-11 14:25 UTCGHSA enrichment
  4. 2026-09-10 16:15 UTCEG score recompute
  5. 2026-09-10 16:15 UTCGHSA enrichment
  6. 2026-09-09 18:06 UTCEG score recompute
  7. 2026-09-09 18:06 UTCGHSA enrichment
  8. 2026-09-08 22:01 UTCEPSS rescore
  9. 2026-09-08 19:58 UTCGHSA enrichment
  10. 2026-09-08 16:09 UTCEG score recompute
  11. 2026-09-08 16:09 UTCGHSA enrichment
  12. 2026-09-08 15:16 UTCEG score recompute
  13. 2026-09-08 15:16 UTCGHSA enrichment
  14. 2026-09-08 03:01 UTCGHSA enrichment
  15. 2026-09-07 04:53 UTCEG score recompute
  16. 2026-09-07 04:53 UTCGHSA enrichment
  17. 2026-09-06 13:48 UTCEPSS rescore
  18. 2026-09-06 06:45 UTCEG score recompute
  19. 2026-09-06 06:45 UTCGHSA enrichment
  20. 2026-09-05 15:31 UTCEPSS rescore
  21. 2026-09-05 08:38 UTCEG score recompute
  22. 2026-09-05 08:38 UTCGHSA enrichment
  23. 2026-09-04 10:31 UTCEG score recompute
  24. 2026-09-04 09:56 UTCEG score recompute
  25. 2026-09-04 09:53 UTCMITRE cvelistV5first tracked

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2026-81666?
CVE-2026-81666 is a medium vulnerability published on September 4, 2026. An integer overflow was found in Corosync's handling of membership commit token messages. The length-validation check for these messages can be bypassed on 32-bit systems due to an integer overflow in the calculation of the expected message length, allowing a crafted network packet to trigger an…
When was CVE-2026-81666 disclosed?
CVE-2026-81666 was first published in the National Vulnerability Database on September 4, 2026, with the most recent update on September 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-81666 actively exploited?
CVE-2026-81666 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 80.4% of all scored CVEs.
What is the CVSS score of CVE-2026-81666?
CVE-2026-81666 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-81666?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-81666, 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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