CVE-2003-0086 in Samba
Summary
by MITRE
The code for writing reg files in Samba before 2.2.8 allows local users to overwrite arbitrary files via a race condition involving chown.
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Analysis
by VulDB Data Team • 08/25/2025
The vulnerability described in CVE-2003-0086 represents a critical race condition flaw within the Samba file sharing implementation that affected versions prior to 2.2.8. This issue specifically impacts the registry file writing functionality where Samba handles reg file operations, creating a window of opportunity for local attackers to exploit system permissions and overwrite arbitrary files on the target system. The vulnerability arises from improper handling of file creation and ownership changes during the registry file writing process, which fundamentally compromises the integrity of the system's file permissions and access controls.
The technical exploitation of this vulnerability leverages a classic race condition scenario where the attacker can manipulate the timing of file operations to gain unauthorized access to file system resources. During the execution of reg file writing operations, Samba creates temporary files and subsequently changes their ownership using the chown system call. The race condition occurs between the creation of these temporary files and the subsequent chown operation, allowing a local attacker to replace the target file with a symbolic link or create a file with malicious content before the system performs the ownership change. This flaw falls under the CWE-362 category of race conditions, specifically involving improper handling of file system operations and process synchronization.
The operational impact of this vulnerability extends beyond simple file overwrites as it provides attackers with a mechanism to escalate privileges and potentially gain unauthorized access to sensitive system resources. Local users who can execute the reg file writing operations can leverage this vulnerability to overwrite critical system files, configuration files, or even files belonging to other users with elevated privileges. The attack vector is particularly concerning because it requires minimal privileges to execute and can be used to compromise the entire system's integrity, making it a significant threat in environments where Samba is deployed as a file sharing service. The vulnerability directly relates to the ATT&CK technique T1068 which involves the exploitation of local privilege escalation opportunities within operating systems.
Mitigation strategies for CVE-2003-0086 require immediate patching of Samba installations to versions 2.2.8 and later where the race condition has been properly addressed. System administrators should implement proper file system permissions and ensure that registry file operations are performed with appropriate access controls and atomic operations. The fix typically involves ensuring that file creation and ownership changes are performed in a synchronized manner, preventing the window where attackers can manipulate the file system between operations. Additionally, monitoring for unauthorized file system changes and implementing proper logging of registry file operations can help detect exploitation attempts. Organizations should also consider restricting local user access to Samba registry operations and implementing the principle of least privilege to minimize the potential impact of such vulnerabilities in their environments.