Cyber Resilience

CVE-2026-40356

Medium

Published: 28 April 2026

Published
28 April 2026
Modified
28 April 2026
KEV Added
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Patch
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CVSS Score v3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
EPSS Score 0.0011 28.6th percentile
Risk Priority 12 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-40356 is a medium-severity Wrap or Wraparound (CWE-191) vulnerability in Cems (inferred from references). Its CVSS base score is 5.9 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 28.6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

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…

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causing the process to terminate in parse_message.

CWE(s)
CWE-191

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
Why these techniques?

Remote unauthenticated integer underflow in gss_accept_sec_context enables direct exploitation of public-facing Kerberos/GSS services, resulting in process crash (application exploitation for DoS).

Confidence: HIGH · MITRE ATT&CK Enterprise v18.1

Affected Assets

Cems
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inferred from references and description; NVD did not file a CPE for this CVE

Mitigating Controls

No mitigating controls mapped yet. The per-CVE control annotator has not reached this CVE.

References