CVE-2025-11561

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 (sssd_krb5_localauth_plugin) 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.

The Red Hat Product Security team has assessed this issue as High severity for domain-joined Linux systems using default SSSD configurations. While the Kerberos local authentication plugin (sssd_krb5_localauth_plugin) is enabled by default, fallback to the an2ln plugin can occur, allowing a domain user who can modify certain Active Directory attributes (such as userPrincipalName or samAccountName) to map to privileged local accounts. This could lead to unauthorized access or elevated privileges on affected Linux hosts. Administrators are advised to review and apply recommended hardening configurations to mitigate this behavior.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

To mitigate this issue, ensure the SSSD Kerberos local authentication plugin (sssd_krb5_localauth_plugin) is configured and the an2ln plugin is disabled by adding "disable = an2ln" in a krb5 include file, for example /var/lib/sss/pubconf/krb5.include.d/localauth_plugin and make sure it is included in the Kerberos configuration. Apply vendor updates and follow Red Hat guidance for SSSD hardening.