CVE-2026-11861 in FreeIPA
Summary
by MITRE • 08/20/2026
A flaw was found in FreeIPA. When a trust relationship is configured between FreeIPA and Active Directory, Active Directory users can bypass authentication for FreeIPA services, including the portal, SMB server, and LDAP directory. This is possible by impersonating a client name in the Ticket Granting Service (TGS) due to FreeIPA services not verifying Privilege Attribute Certificate (PAC) certificates. This vulnerability could allow an authenticated Active Directory user to escalate their privileges within the FreeIPA domain.
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Analysis
by VulDB Data Team • 08/20/2026
The identified vulnerability represents a critical authentication bypass flaw within the FreeIPA identity management system, specifically affecting configurations where trust relationships are established with Microsoft Active Directory environments. The core technical deficiency lies in the handling of Kerberos tickets during service access requests. When an authenticated Active Directory user attempts to interact with FreeIPA services such as the web portal, SMB server, or LDAP directory, they present a Ticket Granting Service ticket issued by their home domain's Key Distribution Center. In standard secure implementations, these tickets contain a Privilege Attribute Certificate that details the security privileges and group memberships of the requesting entity. However, due to this flaw, FreeIPA fails to validate or verify the integrity and contents of these PAC certificates. This oversight allows an attacker who has valid credentials in the Active Directory domain to manipulate the client name field within their TGS request, effectively impersonating a different identity that possesses higher privileges within the FreeIPA realm without needing additional authentication factors.
The operational impact of this vulnerability is severe as it enables direct privilege escalation from a standard user account to administrative or high-privilege roles within the FreeIPA infrastructure. Since the PAC verification is skipped, an attacker can craft requests that appear to originate from trusted service accounts or domain administrators in the eyes of the FreeIPA server. This bypasses the intended access control mechanisms and allows unauthorized modification of directory entries, creation of new privileged users, or complete compromise of identity management policies. The scope extends across all services protected by Kerberos authentication within the trust relationship, meaning that both interactive web interfaces and backend data replication channels are susceptible to exploitation. An attacker leveraging this flaw could gain persistent access to sensitive organizational data stored in LDAP directories or disrupt critical infrastructure managed through FreeIPA.
From a classification perspective, this vulnerability aligns with CWE-287 Improper Authentication, as the system fails to properly verify the identity of an actor before granting access. It also relates closely to CWE-345 Insufficient Verification of Data Authenticity because the PAC certificate is not validated against its expected cryptographic signatures and contents. In terms of adversary tactics, this exploit maps directly to MITRE ATT&CK technique T1078 Valid Accounts, where attackers use legitimate credentials to gain access, combined with T1606 Forged Access Tokens which describes the manipulation of Kerberos tickets to impersonate other users or services. The lack of PAC validation essentially allows token forgery within the context of an existing trust relationship, undermining the foundational security assumptions of mutual authentication between Active Directory and FreeIPA domains.
Mitigation strategies must focus on ensuring that all incoming Kerberos service requests undergo rigorous validation of their embedded privilege attributes. Administrators should immediately apply vendor-provided patches or updates to FreeIPA instances that enforce PAC verification logic before granting access to protected services. In the interim, if patching is not immediately feasible, restricting trust relationships to only those domains with strictly controlled user accounts and implementing network-level segmentation can reduce exposure. Additionally, enabling enhanced logging for Kerberos authentication failures may help detect attempted exploitation of this flaw by monitoring for anomalous TGS requests that exhibit signs of client name impersonation or malformed PAC structures. Regular audits of trust configurations and strict adherence to least privilege principles in both Active Directory and FreeIPA domains are essential to minimize the potential impact should such vulnerabilities be discovered in future updates.