This vulnerability (CVE-2026-40355) affects MIT Kerberos 5 versions prior to 1.22.3. It occurs due to a NULL pointer dereference in the function parse_nego_message when gss_accept_sec_context() is called on systems with a NegoEx mechanism registered. The flaw allows an unauthenticated remote attacker to cause the process to crash, leading to denial of service. The CVSS v3.1 base score is 5.9, reflecting medium severity with network attack vector, high attack complexity, no privileges required, no user interaction, and impact limited to availability.

An unauthenticated remote attacker can exploit this vulnerability to cause the affected process to terminate unexpectedly, resulting in denial of service. There is no impact on confidentiality or integrity according to the CVSS vector. No known exploits are reported in the wild.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since the vulnerability affects versions before 1.22.3, upgrading to version 1.22.3 or later may resolve the issue if confirmed by the vendor. Until an official fix is available, consider disabling the NegoEx mechanism if feasible to prevent triggering the NULL pointer dereference.