---
id: CVE-2026-40355
title: >-
  In MIT Kerberos 5 (aka krb5) before 1.22.3, there is a NULL pointer
  dereference 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 a NULL pointer
  dereference 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 trig…
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-476
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-2026-40355'
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
  - url: >-
      https://cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
tags:
  - nvd
  - cve.org
  - exploit-available
epss: 0.00611
epssPercentile: 0.47909
ingestedAt: '2026-07-08T12:51:00.642Z'
exploitAvailable: true
ssvc:
  exploitation: poc
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-04-28T12:53:15.785781Z'
---

## Overview

In MIT Kerberos 5 (aka krb5) before 1.22.3, there is a NULL pointer dereference 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, causing the process to terminate in parse_nego_message.

## Affected

- `kerberos_5 >= 1.18.0, <= 1.22.2`

## Remediation

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