CVE-2026-40356

HIGHNVD 7.55.9▼
EchelonGraph scoreMEDIUM confidence

Score 5.9 from GitHub Security Advisory published 2026-04-28. NVD baseline CVSS 5.9; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

In MIT Kerberos 5 (aka krb5) before 1.22.3, there is an integer underflow and resultant out-of-bounds read if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, possibly causing the process to terminate in parse_message.

CVSS v3
7.5
EG Score
5.9(medium)
EPSS
39.3%
KEV
Not listed

Published

April 28, 2026

Last Modified

July 8, 2026

Advisory Details (3)

Auto-updated Jun 14, 2026
🔬 Proof of concept available. Upstream fix merged — awaiting tagged release. Sources: github_commit.
generic

Kerberos Security Advisories

https://web.mit.edu/kerberos/advisories/
github_commit

commit 2e75f0d9362f (krb5/krb5)

Fix landed in krb5/krb5 commit 2e75f0d9362f — awaiting tagged release

https://github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f
generic🟡 PoC Available

Advisory - Kerberos (krb5) Two Unauthenticated Network Vulnerabilities: CVE-2026-40355 & CVE-2026-40356 | Cem’s Blog

https://cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html

Vendor Advisories for CVE-2026-40356(11)

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

Patch Availability(9)

Vendor / EcosystemFixed in / PatchReleasedSource
redhatkrb5-0:1.20.1-9.el9_2.62026-06-09redhat
redhatkrb5-0:1.21.1-8.el9_6.22026-06-09redhat
redhatkrb5-0:1.21.1-2.el9_4.52026-06-09redhat
redhatinsights-proxy/insights-proxy-container-rhel9:17804204282026-06-02redhat
redhatrhui5/rhua-rhel9:17797982222026-05-27redhat
redhatkrb5-0:1.21.1-10.el9_82026-05-19redhat
redhatkrb5-0:1.21.3-10.el10_22026-05-19redhat
redhatkrb5-0:1.18.2-34.el8_102026-05-13redhat
redhatkrb5-main-1.22.2-7.hum12026-04-30redhat

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.

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 10× in last 7d / 42× 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 112 total refreshes for this CVE.

  1. 2026-07-12 05:46 UTCEPSS rescore
  2. 2026-07-11 08:27 UTCEPSS rescore
  3. 2026-07-09 19:10 UTCEPSS rescore
  4. 2026-07-08 15:15 UTCEPSS rescore
  5. 2026-07-08 14:36 UTCNVD updateCVSS v3 → 7.5 · severity → HIGH
  6. 2026-07-07 13:46 UTCEPSS rescore
  7. 2026-07-06 16:27 UTCEPSS rescore
  8. 2026-07-06 16:27 UTCEPSS rescore
  9. 2026-07-06 02:23 UTCEPSS rescore
  10. 2026-07-06 02:23 UTCEPSS rescore
  11. 2026-07-05 02:30 UTCEPSS rescore
  12. 2026-07-04 06:31 UTCEPSS rescore
  13. 2026-07-01 15:06 UTCEPSS rescore
  14. 2026-06-30 23:22 UTCEPSS rescore
  15. 2026-06-29 14:06 UTCEPSS rescore
  16. 2026-06-28 14:07 UTCEPSS rescore
  17. 2026-06-28 04:56 UTCEPSS rescore
  18. 2026-06-27 03:08 UTCEPSS rescore
  19. 2026-06-25 13:49 UTCEPSS rescore
  20. 2026-06-25 13:49 UTCEPSS rescore
  21. 2026-06-24 14:05 UTCEPSS rescore
  22. 2026-06-23 21:33 UTCEPSS rescore
  23. 2026-06-22 14:25 UTCEPSS rescore
  24. 2026-06-22 14:25 UTCEPSS rescore
  25. 2026-06-21 14:56 UTCEPSS rescore
Show 75 more
  1. 2026-06-21 14:56 UTCEPSS rescore
  2. 2026-06-21 01:59 UTCEPSS rescore
  3. 2026-06-19 19:25 UTCEPSS rescore
  4. 2026-06-18 17:52 UTCEPSS rescore
  5. 2026-06-18 17:52 UTCEPSS rescore
  6. 2026-06-17 17:53 UTCEPSS rescore
  7. 2026-06-16 17:52 UTCEPSS rescore
  8. 2026-06-15 17:49 UTCEPSS rescore
  9. 2026-06-14 09:51 UTCEG score recompute
  10. 2026-06-14 09:51 UTCVendor advisory
  11. 2026-06-14 09:51 UTCGHSA enrichment
  12. 2026-06-13 23:00 UTCEPSS rescore
  13. 2026-06-12 23:12 UTCEPSS rescore
  14. 2026-06-12 23:12 UTCEPSS rescore
  15. 2026-06-12 10:38 UTCEG score recompute
  16. 2026-06-12 10:38 UTCVendor advisory
  17. 2026-06-12 10:38 UTCGHSA enrichment
  18. 2026-06-11 14:00 UTCEPSS rescore
  19. 2026-06-11 06:53 UTCEG score recompute
  20. 2026-06-11 06:53 UTCVendor advisory
  21. 2026-06-11 06:53 UTCGHSA enrichment
  22. 2026-06-10 22:18 UTCEPSS rescore
  23. 2026-06-10 13:22 UTCEPSS rescore
  24. 2026-06-10 13:22 UTCEPSS rescore
  25. 2026-06-10 04:57 UTCEG score recompute
  26. 2026-06-10 04:57 UTCVendor advisory
  27. 2026-06-10 04:57 UTCGHSA enrichment
  28. 2026-06-09 03:02 UTCEG score recompute
  29. 2026-06-09 03:02 UTCVendor advisory
  30. 2026-06-09 03:02 UTCGHSA enrichment
  31. 2026-06-08 14:17 UTCEPSS rescore
  32. 2026-06-08 14:17 UTCEPSS rescore
  33. 2026-06-07 23:59 UTCEG score recompute
  34. 2026-06-07 23:59 UTCVendor advisory
  35. 2026-06-07 23:59 UTCGHSA enrichment
  36. 2026-06-07 15:25 UTCEPSS rescore
  37. 2026-06-07 15:25 UTCEPSS rescore
  38. 2026-06-06 21:51 UTCEG score recompute
  39. 2026-06-06 21:51 UTCVendor advisory
  40. 2026-06-06 21:51 UTCGHSA enrichment
  41. 2026-06-06 13:47 UTCEPSS rescore
  42. 2026-06-06 13:47 UTCEPSS rescore
  43. 2026-06-05 22:47 UTCEPSS rescore
  44. 2026-06-05 19:16 UTCEG score recompute
  45. 2026-06-05 19:16 UTCVendor advisory
  46. 2026-06-05 19:16 UTCGHSA enrichment
  47. 2026-06-05 06:10 UTCEPSS rescore
  48. 2026-06-05 06:10 UTCEPSS rescore
  49. 2026-06-04 17:21 UTCEG score recompute
  50. 2026-06-04 17:21 UTCVendor advisory
  51. 2026-06-04 17:21 UTCGHSA enrichment
  52. 2026-06-04 13:12 UTCEPSS rescore
  53. 2026-06-04 13:12 UTCEPSS rescore
  54. 2026-06-03 15:26 UTCEG score recompute
  55. 2026-06-03 15:26 UTCVendor advisory
  56. 2026-06-03 15:26 UTCGHSA enrichment
  57. 2026-06-02 20:13 UTCEPSS rescore
  58. 2026-06-02 13:22 UTCEG score recompute
  59. 2026-06-02 13:22 UTCVendor advisory
  60. 2026-06-02 13:22 UTCGHSA enrichment
  61. 2026-06-01 13:52 UTCEPSS rescore
  62. 2026-06-01 13:52 UTCEPSS rescore
  63. 2026-06-01 13:51 UTCEPSS rescore
  64. 2026-06-01 11:27 UTCEG score recompute
  65. 2026-06-01 11:27 UTCVendor advisory
  66. 2026-06-01 11:27 UTCGHSA enrichment
  67. 2026-05-31 22:30 UTCEPSS rescore
  68. 2026-05-31 22:30 UTCEPSS rescore
  69. 2026-05-31 00:16 UTCEPSS rescore
  70. 2026-05-31 00:16 UTCEPSS rescore
  71. 2026-05-31 00:16 UTCEPSS rescore
  72. 2026-05-29 13:44 UTCEPSS rescore
  73. 2026-05-29 13:44 UTCEPSS rescore
  74. 2026-05-28 13:44 UTCEPSS rescore
  75. 2026-05-28 13:44 UTCEPSS rescore

Frequently asked(5)

What is CVE-2026-40356?
CVE-2026-40356 is a high vulnerability published on April 28, 2026. In MIT Kerberos 5 (aka krb5) before 1.22.3, there is an integer underflow and resultant out-of-bounds read if an application calls gssacceptseccontext() on a system with a NegoEx mechanism registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, possibly causing the process…
When was CVE-2026-40356 disclosed?
CVE-2026-40356 was first published in the National Vulnerability Database on April 28, 2026, with the most recent update on July 8, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-40356 actively exploited?
CVE-2026-40356 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 39.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2026-40356?
CVE-2026-40356 has a CVSS v3 base score of 7.5 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 5.9.
How do I remediate CVE-2026-40356?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-40356, 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

Explore the affected products and dependency analysis for CVE-2026-40356

Explore →

Is Your Infrastructure Affected by CVE-2026-40356?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs