CVE-2008-3789 in Samba
Summary
by MITRE
Samba 3.2.0 uses weak permissions (0666) for the (1) group_mapping.tdb and (2) group_mapping.ldb files, which allows local users to modify the membership of Unix groups.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/17/2019
The vulnerability described in CVE-2008-3789 affects Samba version 3.2.0 and represents a critical access control flaw that undermines the security of Unix group management within Samba environments. This issue stems from the improper configuration of file permissions for critical group mapping database files, specifically group_mapping.tdb and group_mapping.ldb, which are essential components for maintaining group membership relationships between Windows and Unix systems. The flaw allows local attackers with minimal privileges to manipulate group memberships by directly modifying these database files, effectively bypassing the normal access controls and authentication mechanisms that should protect such sensitive configuration data.
The technical implementation of this vulnerability involves the use of weak file permissions set to 0666, which grants read and write access to all users on the system. This permission level violates fundamental security principles and creates an attack surface that enables unauthorized modification of group membership information. The group_mapping.tdb and group_mapping.ldb files serve as the primary storage mechanisms for mapping Windows group identities to Unix group identifiers, making them critical targets for privilege escalation attacks. When these files are accessible with such permissive permissions, any local user can modify the database entries to add themselves or other users to privileged Unix groups, effectively elevating their system privileges without proper authentication or authorization.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it fundamentally compromises the integrity of the Unix group management system within Samba environments. Attackers can leverage this weakness to gain access to resources, files, and system functions that should be restricted to specific user groups, potentially leading to complete system compromise. The vulnerability affects systems where Samba serves as a file server, domain controller, or member server in mixed Windows and Unix environments, making it particularly dangerous in enterprise settings where proper access controls are essential for maintaining security boundaries. This flaw represents a significant weakness in the principle of least privilege, as it allows any local user to modify critical group membership information that controls access to system resources.
Mitigation strategies for CVE-2008-3789 should focus on immediate permission corrections combined with broader security hardening measures. The primary fix involves changing the file permissions of group_mapping.tdb and group_mapping.ldb files to restrictive settings that only permit access to the Samba service account or root user. This approach aligns with security best practices outlined in the Center for Internet Security (CIS) benchmarks and follows the principle of least privilege as defined in the National Institute of Standards and Technology (NIST) security frameworks. Additionally, system administrators should implement regular monitoring of these files for unauthorized modifications and consider implementing file integrity checking mechanisms to detect potential tampering. The vulnerability demonstrates the importance of proper file permission management and access control configuration as outlined in the Common Weakness Enumeration (CWE) catalog under CWE-73, which addresses insufficient permissions for critical resources. Organizations should also consider implementing the ATT&CK framework's privilege escalation techniques to better understand and defend against such attack vectors, particularly focusing on the persistence and privilege escalation categories that leverage weak file permissions to gain elevated system access.