---
id: CVE-2026-40356
title: >-
  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
summary: >-
  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
  unauthenticat…
severity: medium
cvss: 5.9
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'
cwe:
  - CWE-191
vendor: mit
product: kerberos_5
affected:
  - 'kerberos_5 >= 1.18.0, <= 1.22.2'
published: '2026-04-28'
updated: '2026-07-08'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-40356'
references:
  - url: >-
      https://cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html
    label: cve@mitre.org
  - url: >-
      https://github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f
    label: cve@mitre.org
  - url: 'https://web.mit.edu/kerberos/advisories/'
    label: cve@mitre.org
tags:
  - nvd
epss: 0.00604
epssPercentile: 0.47613
ingestedAt: '2026-07-08T12:51:00.671Z'
---

## Overview

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.

## Affected

- `kerberos_5 >= 1.18.0, <= 1.22.2`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.