CVE-2025-11561 is a vulnerability in the integration between Active Directory (AD) and the System Security Services Daemon (SSSD) on Linux systems, notably Red Hat Enterprise Linux 10. SSSD facilitates centralized identity and authentication management, including Kerberos authentication for domain-joined Linux hosts. By default, the Kerberos local authentication plugin (sssd_krb5_localauth_plugin) is enabled to authenticate users locally. However, due to a design flaw, this plugin can fall back to the an2ln plugin under certain conditions. This fallback mechanism is exploitable if an attacker has the ability to modify specific AD attributes such as userPrincipalName or samAccountName. These attributes are critical identifiers in AD and are used during authentication and authorization processes. By altering these attributes, an attacker can impersonate privileged users, effectively bypassing intended access controls. This leads to unauthorized access and privilege escalation on Linux hosts that are joined to the AD domain. The vulnerability requires the attacker to have some level of permission to modify AD attributes, which implies a prerequisite level of access but does not require user interaction or complex attack vectors. The CVSS 3.1 score of 8.8 reflects the vulnerability’s high impact across confidentiality, integrity, and availability, with network attack vector, low attack complexity, and privileges required. Although no exploits have been reported in the wild yet, the potential for serious compromise in enterprise environments is significant, especially where Linux systems are integrated tightly with AD for authentication and authorization.

For European organizations, the impact of CVE-2025-11561 is substantial, particularly those relying on Red Hat Enterprise Linux 10 systems integrated with Active Directory for identity management. Successful exploitation can lead to unauthorized access to sensitive systems, privilege escalation, and potential lateral movement within corporate networks. This threatens the confidentiality of sensitive data, the integrity of user and system accounts, and the availability of critical services. Organizations in sectors such as finance, government, healthcare, and critical infrastructure, which often use Linux-AD integration for secure authentication, face increased risk of targeted attacks. The ability to impersonate privileged users could facilitate data breaches, sabotage, or espionage. Additionally, the vulnerability could undermine trust in identity management systems and complicate compliance with European data protection regulations such as GDPR, due to unauthorized access incidents. The absence of known exploits in the wild provides a window for proactive mitigation, but the high CVSS score underscores the urgency of addressing this flaw before it can be weaponized.

To mitigate CVE-2025-11561 effectively, European organizations should implement the following specific measures: 1) Immediately apply any patches or updates released by Red Hat addressing this vulnerability once available. 2) Restrict permissions in Active Directory to limit which users or groups can modify critical attributes like userPrincipalName and samAccountName, enforcing the principle of least privilege. 3) Audit and monitor changes to AD attributes continuously to detect unauthorized modifications promptly. 4) Review and harden SSSD configuration to disable or control fallback mechanisms such as the an2ln plugin if feasible, reducing attack surface. 5) Employ multi-factor authentication (MFA) for privileged accounts to add an additional layer of security beyond attribute-based authentication. 6) Conduct regular security assessments and penetration tests focusing on AD-Linux integration points to identify and remediate weaknesses. 7) Educate system administrators and security teams about this vulnerability and the importance of monitoring AD attribute changes. 8) Implement network segmentation to limit the impact of compromised Linux hosts within the domain. These targeted actions go beyond generic advice by focusing on the specific attack vector and environment involved in this vulnerability.