CVE-2012-6150 in Samba
Summary
by MITRE
The winbind_name_list_to_sid_string_list function in nsswitch/pam_winbind.c in Samba through 4.1.2 handles invalid require_membership_of group names by accepting authentication by any user, which allows remote authenticated users to bypass intended access restrictions in opportunistic circumstances by leveraging an administrator s pam_winbind configuration-file mistake.
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Analysis
by VulDB Data Team • 01/11/2022
The vulnerability identified as CVE-2012-6150 represents a critical authentication bypass flaw within the Samba network services implementation. This issue affects Samba versions through 4.1.2 and specifically targets the winbind_name_list_to_sid_string_list function located in the nsswitch/pam_winbind.c file. The flaw manifests when the system processes invalid group names specified in the require_membership_of parameter within the pam_winbind configuration, creating a security weakness that undermines the intended access control mechanisms.
The technical root cause of this vulnerability lies in the improper handling of malformed group names during the authentication process. When administrators configure pam_winbind with invalid require_membership_of group specifications, the function fails to properly validate these inputs and instead falls back to a permissive authentication model. This behavior allows any authenticated user to bypass the intended group membership restrictions, effectively rendering the access control policies ineffective. The vulnerability operates at the PAM (Pluggable Authentication Modules) layer, where authentication decisions are made, making it particularly dangerous as it can be exploited by remote authenticated users without requiring elevated privileges or direct system access.
The operational impact of this vulnerability extends beyond simple authentication bypass to encompass broader security implications within enterprise environments that rely on Samba for Windows domain integration. Organizations using Samba for authentication services may experience unauthorized access to resources that should be restricted to specific user groups, potentially leading to data breaches, privilege escalation, and unauthorized system modifications. The vulnerability is particularly concerning because it can be exploited opportunistically, meaning attackers can leverage misconfigurations that administrators might not immediately notice or correct, creating a window of opportunity for unauthorized access.
From a cybersecurity perspective, this vulnerability aligns with CWE-284 (Improper Access Control) and can be mapped to ATT&CK technique T1078 (Valid Accounts) and T1566 (Phishing). The flaw demonstrates how configuration errors in authentication systems can create security weaknesses that adversaries can exploit to gain unauthorized access. Organizations should prioritize immediate remediation through Samba version updates to 4.1.3 or later, which contain the necessary patches to address the improper input validation. Additionally, security teams should conduct comprehensive audits of all pam_winbind configuration files to identify and correct any require_membership_of parameter specifications that may contain invalid group names. The vulnerability underscores the importance of proper configuration management and input validation in authentication systems, as even seemingly minor configuration mistakes can have significant security implications.