This vulnerability in SSSD's PAM responder allows a local attacker with low privileges to cause a denial of service by sending a crafted PAM request that omits the service item when pam_app_services is enabled in the configuration. The flaw triggers a NULL pointer dereference, crashing the PAM responder process and interrupting authentication services. The issue requires local access and a non-default configuration. The vulnerability has a CVSS 3.1 base score of 5.5 (medium severity) and does not impact confidentiality or integrity, only availability.

An authenticated local attacker can cause the PAM responder to crash by exploiting a NULL pointer dereference, resulting in denial of service and disruption of authentication services. There is no impact on confidentiality or integrity. The default configuration is not affected, so only systems with pam_app_services enabled are vulnerable.

Red Hat advises avoiding the use of the pam_app_services configuration in the [pam] section of /etc/sssd/sssd.conf unless operationally required. If pam_app_services is configured, remove or comment out the pam_app_services line and restart the sssd service using 'systemctl restart sssd'. Restarting the service may temporarily interrupt authentication and authorization services. Patch status is currently under investigation; check the Red Hat advisory for updates.