Critical [CVE-2026-11861] Obtaining TGS with impersonating cname through trust relationships
This critical-severity Red Hat Linux advisory covers CVE-2026-11861 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
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.
This vulnerability is rated as Moderate because practical exploitation is significantly constrained by conditions that are unlikely to be met in most production environments.
The attack requires a cross-realm trust to be configured between FreeIPA and Active Directory, the attacker must already hold a valid Active Directory account, and the impersonation technique depends on the ability to register a duplicate or conflicting Service Principal Name (SPN) in the Active Directory forest.
Microsoft addressed this prerequisite by enforcing SPN and UPN uniqueness constraints on Windows Server 2012 R2 domain controllers with MSKB-3070083 applied, and by default on Windows 11 version 22H2 and later.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 2 hours ago·verify at source
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