CVE-2004-0186 in Samba
Summary
by MITRE
smbmnt in Samba 2.x and 3.x on Linux 2.6, when installed setuid, allows local users to gain root privileges by mounting a Samba share that contains a setuid root program, whose setuid attributes are not cleared when the share is mounted.
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Analysis
by VulDB Data Team • 12/14/2024
The vulnerability described in CVE-2004-0186 represents a critical privilege escalation flaw within the Samba file sharing implementation that affected versions 2.x and 3.x across Linux 2.6 systems. This issue specifically manifests when the smbmnt utility is installed with setuid root permissions, creating a dangerous attack surface that local users can exploit to gain administrative privileges. The core problem lies in how Samba handles file permissions during the mounting process of remote shares, particularly when those shares contain programs with elevated privileges.
The technical exploitation of this vulnerability occurs through a fundamental failure in permission handling within the Samba mounting mechanism. When a local user mounts a Samba share containing a setuid root program, the system fails to properly clear the setuid attributes of these files during the mounting process. This oversight allows the mounted program to retain its elevated privileges, enabling the local attacker to execute it with root permissions. The vulnerability is classified under CWE-276 as improper file permissions and falls under the ATT&CK technique T1548.1 for privilege escalation through setuid binaries. The flaw essentially creates a path where user-controlled file systems can maintain or inherit root-level permissions, bypassing normal security boundaries that should prevent such privilege escalation.
The operational impact of this vulnerability extends beyond simple local privilege escalation, as it provides attackers with complete system control through the execution of setuid programs. This vulnerability is particularly dangerous because it requires minimal user interaction and can be exploited without network access once the initial foothold is established. Attackers can leverage this weakness to execute malicious code with root privileges, potentially leading to full system compromise, data exfiltration, or persistence mechanisms. The vulnerability affects systems where Samba is configured to run with setuid permissions, which was common in many enterprise environments during the early 2000s, making it a widespread concern across numerous organizations.
Mitigation strategies for this vulnerability require immediate action to address the underlying permission issues within Samba implementations. The primary solution involves either removing the setuid bit from the smbmnt utility or ensuring that Samba properly clears setuid attributes during mount operations. System administrators should also implement proper file permission controls and regularly audit setuid binaries on affected systems. The vulnerability highlights the importance of proper privilege separation and file system security controls, as outlined in security frameworks such as the CIS Linux Benchmark and NIST guidelines for secure system configuration. Additionally, organizations should consider implementing mandatory access controls and privilege monitoring to detect unauthorized setuid binary execution. The remediation process must include thorough testing to ensure that Samba functionality remains intact while eliminating the security risk. This vulnerability serves as a critical reminder of the dangers posed by improper privilege management and the need for comprehensive security auditing of system utilities that handle user input and file operations.