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