Integer Underflow in MIT Kerberos 5 gss_accept_sec_context Causes Crash

Publication date: 2026-04-28

Last updated on: 2026-07-08

Assigner: MITRE

Description

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 Scores

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Meta Information

Published

2026-04-28

Last Modified

2026-07-08

Generated

2026-07-27

AI Q&A

2026-04-28

EPSS Evaluated

2026-07-25

NVD

CVE-2026-40356

EUVD

EUVD-2026-25993

Affected Vendors & Products

Vendor	Product	Version / Range
mit	kerberos_5	From 1.18.0 (inc) to 1.22.2 (inc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-191	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.

Attack-Flow Graph

Executive Summary

This vulnerability exists in MIT Kerberos 5 versions before 1.22.3. It involves an integer underflow and an out-of-bounds read that occurs when an application calls the function gss_accept_sec_context() on a system where a NegoEx mechanism is registered in /etc/gss/mech. An unauthenticated remote attacker can exploit this flaw, potentially causing the affected process to terminate unexpectedly during the parse_message operation.

Impact Analysis

The primary impact of this vulnerability is that an unauthenticated remote attacker can cause the affected process to terminate unexpectedly, leading to a denial of service (DoS) condition. This could disrupt services relying on MIT Kerberos 5 authentication mechanisms.

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