Gssproxy: gssproxy: null pointer dereference in gssx_init_sec_context crashes daemon

Overview

A NULL pointer dereference vulnerability was found in gssproxy. When a GSSX_INIT_SEC_CONTEXT request is received with the target_name field absent, the daemon dereferences the resulting NULL pointer and crashes. The request requires no authentication, allowing any local user to crash the gssproxy daemon via its Unix socket. The daemon does not automatically restart, resulting in a persistent denial of service that also affects dependent services such as Kerberized NFS and IdM.

Affected

• gssproxy (all versions)
• gssproxy (all versions)
• gssproxy (all versions)
• gssproxy (all versions)
• openshift/ose-rhel-coreos-8 (all versions)
• openshift/ose-rhel-coreos-9 (all versions)

Remediation

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

Workarounds

There is no way to fully mitigate this vulnerability without applying a code fix. The gssproxy Unix socket must be world-accessible for normal operation, and the default configuration accepts connections from any local user.

As a partial workaround, administrators can add "Restart=on-failure" to the gssproxy systemd unit to enable automatic restarts after a crash. This does not prevent the crash but limits the denial-of-service window. Note that a persistent attacker can still outpace the restart cycle.