A local attacker can trigger a denial of service by sending a crafted Pluggable Authentication Module (PAM) request that contains a zero‑length authentication token to the sssd PAM responder socket. Because the responder fails to validate the length of the token, it attempts to read beyond the end of the supplied buffer, causing a crash of the PAM responder process. The crash terminates the authentication service and may prevent subsequent authentication operations, thereby disrupting services that depend on sssd.

Red Hat Enterprise Linux releases 6, 7, 8, 9, and 10 and Red Hat OpenShift Container Platform 4 are affected. Users of these distributions that run the default sssd component should check for the latest security update.

The CVSS score of 5.5 indicates moderate severity. EPSS data are not available and the vulnerability is not listed in CISA’s KEV catalog, implying no widespread exploitation has been reported. The flaw is local; an attacker would need local access to the PAM responder socket to send the crafted request. Because the impact is a service crash rather than privilege escalation or data theft, the primary risk is availability degradation for local users or services that rely on sssd authentication.