CVE-2000-0052 in Linux
Summary
by MITRE
Red Hat userhelper program in the usermode package allows local users to gain root access via PAM and a .. (dot dot) attack.
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Analysis
by VulDB Data Team • 11/28/2024
The vulnerability described in CVE-2000-0052 represents a critical privilege escalation flaw within the Red Hat userhelper program that was part of the usermode package. This issue specifically exploited weaknesses in how the program handled path traversal attacks combined with PAM authentication mechanisms. The vulnerability allowed local attackers to escalate their privileges from standard user level to root access through a carefully crafted directory traversal attack that manipulated the program's path resolution behavior.
The technical exploitation mechanism relied on the userhelper program's improper handling of directory traversal sequences using the ".." (dot dot) notation. When the program processed user input containing these traversal sequences, it failed to properly sanitize or validate the paths, allowing attackers to navigate outside the intended directory boundaries. This flaw was particularly dangerous because it occurred within a program that had elevated privileges and was designed to interact with PAM authentication modules. The combination of the path traversal vulnerability with PAM integration created a perfect storm for privilege escalation, as the program could be tricked into executing commands or accessing files with root-level permissions.
The operational impact of this vulnerability was severe for systems running affected versions of Red Hat Linux. Local users who could execute the userhelper program or influence its execution paths could gain complete system control without requiring prior authentication. This represented a significant compromise of system security, as the attack vector required minimal privileges to initiate and could be executed without network access. The vulnerability essentially provided a backdoor method for privilege escalation that bypassed normal authentication mechanisms, making it particularly dangerous in multi-user environments where system administrators needed to trust local users.
This vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The flaw also relates to CWE-78, which covers improper neutralization of special elements used in OS commands, as the path traversal could potentially lead to command injection scenarios. From an ATT&CK framework perspective, this vulnerability maps to T1068, which covers "Exploitation for Privilege Escalation," and T1548.001, covering "Abuse of Functionality" through the exploitation of programmatic weaknesses. The attack pattern demonstrates how seemingly benign program functionality can be leveraged for malicious purposes when proper input validation and privilege separation are not implemented.
Mitigation strategies for this vulnerability required immediate patching of the usermode package and implementation of proper path validation mechanisms. System administrators needed to ensure that all path traversal sequences were properly sanitized before being processed by privileged programs. The fix involved implementing strict input validation and ensuring that programs like userhelper properly checked for and rejected directory traversal attempts. Additionally, privilege separation principles should have been enforced to prevent programs from operating with unnecessary elevated privileges. Regular security audits and code reviews focusing on input validation and path handling became essential practices to prevent similar vulnerabilities in other system components. The incident highlighted the importance of secure coding practices and the need for comprehensive security testing of programs that handle user input in privileged contexts.