A flaw was found in sssd. When authenticating with a YubiKey, the SSSD PAM responder can crash due to a use-after-free vulnerability, where a memory pointer is incorrectly handled. A local attacker could exploit this flaw by manipulating smartcard or YubiKey contents, leading to a denial of service that disrupts authentication. This vulnerability also presents a potential for privilege escalation, although it is difficult to exploit.

A flaw was found in the integration of Active Directory and the System Security Services Daemon (SSSD) on Linux systems. In default configurations, the Kerberos local authentication plugin (sssdkrb5localauthplugin) is enabled, but a fallback to the an2ln plugin is possible. This fallback allows an attacker with permission to modify certain AD attributes (such as userPrincipalName or samAccountName) to impersonate privileged users, potentially resulting in unauthorized access or privilege escalation on domain-joined Linux hosts.

A flaw was found in SSSD. The sssnssprotocolfillinitgr() function in the NSS responder (src/responder/nss/nssprotocolgrent.c) pre-allocates the reply packet for all group entries using ssspacketgrow() but does not shrink the packet when groups are skipped (non-POSIX, incomplete, or filtered groups). ssspacketgrow() uses tallocreallocsize(), which does not zero-fill newly allocated memory. The trailing unwritten bytes therefore contain uninitialized heap data from the sssdnss process and are transmitted to the client at the grown packet length. A local attacker can exploit this by sending SSSNSSINITGR (0x0026) requests to the world-writable NSS responder socket (/var/lib/sss/pipes/nss), receiving uninitialized heap content in the reply tail. Through heap grooming (for example, a preceding getpwnam query), the leak can disclose other users' cached directory records and process heap pointers. The leaked data is limited to the sssdnss heap (directory-level information); credentials reside in separate sssdpam and sssdbe processes. Reported via PSIRTSUPT-20553 by BreachX Zero Day Labs.

A flaw was found in SSSD. The sssnssprotocolfillinitgr() function in the NSS responder (src/responder/nss/nssprotocolgrent.c) pre-allocates the reply packet for all group entries using ssspacketgrow() but does not shrink the packet when groups are skipped (non-POSIX, incomplete, or filtered groups). ssspacketgrow() uses tallocreallocsize(), which does not zero-fill newly allocated memory. The trailing unwritten bytes therefore contain uninitialized heap data from the sssdnss process and are transmitted to the client at the grown packet length. A local attacker can exploit this by sending SSSNSSINITGR (0x0026) requests to the world-writable NSS responder socket (/var/lib/sss/pipes/nss), receiving uninitialized heap content in the reply tail. Through heap grooming (for example, a preceding getpwnam query), the leak can disclose other users' cached directory records and process heap pointers. The leaked data is limited to the sssdnss heap (directory-level information); credentials reside in separate sssdpam and sssdbe processes. Reported via PSIRTSUPT-20553 by BreachX Zero Day Labs.