CVE-2015-8467 in Samba
Summary
by MITRE
The samldb_check_user_account_control_acl function in dsdb/samdb/ldb_modules/samldb.c in Samba 4.x before 4.1.22, 4.2.x before 4.2.7, and 4.3.x before 4.3.3 does not properly check for administrative privileges during creation of machine accounts, which allows remote authenticated users to bypass intended access restrictions by leveraging the existence of a domain with both a Samba DC and a Windows DC, a similar issue to CVE-2015-2535.
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Analysis
by VulDB Data Team • 07/01/2022
The vulnerability identified as CVE-2015-8467 resides within the Samba directory services implementation and specifically targets the samldb_check_user_account_control_acl function located in dsdb/samdb/ldb_modules/samldb.c. This flaw affects Samba versions prior to 4.1.22, 4.2.7, and 4.3.3 across multiple release branches, creating a significant security risk in environments where Samba domain controllers operate alongside Windows domain controllers. The vulnerability stems from improper privilege validation during the creation of machine accounts, which represents a critical weakness in the access control mechanisms that should enforce administrative boundaries between different domain controller types.
The technical flaw manifests when Samba processes machine account creation requests and fails to adequately verify whether the requesting user possesses the necessary administrative privileges. This oversight allows authenticated users to manipulate account control flags during machine account creation, effectively bypassing intended access restrictions that should prevent non-administrative users from performing privileged operations. The vulnerability becomes particularly dangerous in hybrid environments where both Samba and Windows domain controllers coexist, as it exploits the trust relationship between these different implementations. The flaw is categorized under CWE-284, which specifically addresses improper access control, and aligns with ATT&CK technique T1078.002 for Valid Accounts and T1068 for Exploitation for Privilege Escalation, as it enables unauthorized users to gain elevated privileges through legitimate account creation processes.
The operational impact of CVE-2015-8467 extends beyond simple privilege escalation, as it enables attackers to potentially manipulate domain security policies and access restricted resources. In environments with mixed domain controller implementations, an authenticated attacker could leverage this vulnerability to create machine accounts with elevated privileges, effectively compromising the security boundary between different domain controller types. This weakness could allow for lateral movement within the domain, privilege escalation to domain administrator accounts, and potential access to sensitive organizational data. The vulnerability's similarity to CVE-2015-2535 indicates a pattern of insufficient privilege validation in Samba's directory services implementation, suggesting that organizations running Samba domain controllers in hybrid environments face ongoing risks from related flaws.
Organizations should immediately implement mitigations including upgrading to patched Samba versions, implementing additional access controls on machine account creation processes, and monitoring for unauthorized machine account modifications. Network segmentation and privilege separation measures can help reduce the impact if exploitation occurs, while comprehensive auditing of domain controller activities should be implemented to detect potential abuse of this vulnerability. The remediation process should include thorough vulnerability assessments of hybrid domain environments, particularly focusing on the interaction between Samba and Windows domain controllers. Security teams should also consider implementing additional monitoring for account creation events and privilege changes, as the vulnerability could enable attackers to establish persistent access through machine accounts that bypass normal administrative controls.