MIT Kerberos 5 1.22.3 CVE-2026-40356: Integer Underflow in gss_accept_sec_context
CVE-2026-40356 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 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.
Vulnerability Analysis
CVE-2026-40356 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is consided to have a high level of attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
What is an Integer underflow Vulnerability?
The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result. This can happen in signed and unsigned cases.
CVE-2026-40356 has been classified to as an Integer underflow vulnerability or weakness.
Products Associated with CVE-2026-40356
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Affected Versions
MIT Kerberos 5:- Version 1.18 and below 1.22.3 is affected.