A vulnerability was found in SSSD, in the libsss_certmap functionality. PKINIT enables a client to authenticate to the KDC using an X.509 certificate and the corresponding private key, rather than a passphrase or keytab. FreeIPA uses mapping rules to map a certificate presented during a PKINIT authentication request to the corresponding principal. The mapping filter is vulnerable to LDAP filter injection. The search result can be influenced by values in the certificate, which may be attacker controlled. In the most extreme case, an attacker could gain control of the admin account, leading to full domain takeover.