A flaw in SSSD allows a remote attacker to cause a denial of service by submitting a certificate that lacks the required Microsoft Security Identifier (SID) extension. In configurations that employ SID‑based certificate mapping rules, the service attempts to access the missing extension before verification, leading to a process crash during authentication or lookup. The vulnerability is categorized as CWE‑476, a null or invalid pointer dereference.

Red Hat Enterprise Linux versions 6 through 10 and Red Hat OpenShift Container Platform 4 are affected, as SSSD is deployed across these platforms. The issue specifically targets deployments that use "{sid}" or "{sid.rid}" expansion templates within LDAPU1 certificate mapping rules.

The CVSS score of 5.9 indicates medium severity, and the EPSS score is not available. The vulnerability is not listed in CISA KEV. Based on the description, the likely attack vector is remote authentication: an attacker sends a forged certificate lacking the SID extension over a trusted channel to a system running SSSD. This can force the service to crash, disrupting identity lookup and authentication until the service is restarted.