CVE-2025-11561 is a vulnerability discovered in the integration between Active Directory (AD) and the System Security Services Daemon (SSSD) on Linux systems, notably Red Hat Enterprise Linux 10. The issue stems from the default configuration where the Kerberos local authentication plugin (sssd_krb5_localauth_plugin) is enabled, but if it fails, the system falls back to the an2ln plugin. This fallback mechanism is insecure because it allows an attacker with the ability to modify specific AD attributes—namely userPrincipalName or samAccountName—to impersonate privileged users on the Linux host. These attributes are critical identifiers in AD that map users to their credentials and permissions. By altering these, an attacker can effectively escalate privileges or gain unauthorized access to domain-joined Linux systems. The vulnerability requires the attacker to have some level of permission to modify AD attributes, which implies a prerequisite level of access, but no user interaction is needed to exploit it. The CVSS 3.1 score of 8.8 reflects the vulnerability’s high impact on confidentiality, integrity, and availability, combined with low attack complexity and network attack vector. While no exploits are currently known in the wild, the flaw poses a significant risk in environments where AD and SSSD are integrated for authentication, especially in enterprise Linux deployments. The vulnerability highlights the risks of fallback authentication mechanisms and the importance of strict AD attribute modification controls.

For European organizations, the impact of CVE-2025-11561 can be substantial, particularly for enterprises and government agencies that rely on Red Hat Enterprise Linux 10 systems joined to Active Directory domains. Exploitation could lead to unauthorized access to sensitive systems, privilege escalation, and potential lateral movement within corporate networks. This could compromise confidential data, disrupt critical services, and undermine trust in identity and access management infrastructure. The vulnerability affects the integrity and availability of authentication processes, potentially allowing attackers to bypass security controls and gain persistent footholds. Organizations in sectors such as finance, healthcare, telecommunications, and public administration, which often use AD-joined Linux servers for critical applications, are at heightened risk. The ability to impersonate privileged users could also facilitate further attacks, including data exfiltration, ransomware deployment, or sabotage. Given the network attack vector and no requirement for user interaction, the threat can be exploited remotely, increasing its severity in distributed and cloud-connected environments common in Europe.

To mitigate CVE-2025-11561, organizations should immediately review and restrict permissions related to modifying AD attributes such as userPrincipalName and samAccountName, ensuring only highly trusted administrators have such rights. Applying vendor patches or updates from Red Hat as soon as they become available is critical to address the underlying vulnerability. In the interim, consider disabling the fallback to the an2ln plugin in SSSD configurations if feasible, or enforce stricter authentication plugin policies to prevent fallback exploitation. Conduct thorough audits of AD attribute changes and implement monitoring to detect suspicious modifications. Employ network segmentation and least privilege principles to limit the potential impact of compromised accounts. Additionally, enhance logging and alerting on authentication anomalies within domain-joined Linux hosts. Organizations should also review their incident response plans to include scenarios involving AD attribute manipulation and privilege escalation via SSSD. Finally, educating administrators about the risks of improper privilege delegation in AD environments can reduce the likelihood of accidental exposure.