CVE-2000-0077 in HP-UX
Summary
by MITRE
The October 1998 version of the HP-UX aserver program allows local users to gain privileges by specifying an alternate PATH which aserver uses to find the ps and grep commands.
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Analysis
by VulDB Data Team • 10/04/2024
The vulnerability described in CVE-2000-0077 represents a classic privilege escalation flaw in the HP-UX operating system's aserver program from October 1998. This issue demonstrates how insecure command execution practices can lead to unauthorized privilege elevation within Unix-like systems. The aserver program, which serves as a system service for managing printer queues and related printing functions, was designed to execute system commands for process monitoring and status checking. However, the implementation contained a critical design flaw that allowed local attackers to manipulate the program's execution environment through the PATH variable.
The technical exploitation of this vulnerability relies on the program's improper handling of environment variables during command execution. When aserver needs to execute the ps and grep commands to monitor system processes, it does not explicitly specify the full path to these utilities. Instead, it relies on the system's PATH environment variable to locate the executables. This design decision creates a path traversal vulnerability that local users can exploit by manipulating their environment to insert malicious executables into the PATH at a higher precedence level than the legitimate system binaries. The vulnerability specifically affects the aserver program's behavior when it attempts to execute the ps and grep commands, making it a command injection issue with privilege escalation implications.
The operational impact of this vulnerability extends beyond simple local privilege escalation, as it provides attackers with elevated system access that could lead to complete system compromise. An attacker with local access can create malicious versions of ps and grep commands in a directory they control, place that directory at the beginning of the PATH, and then execute aserver to trigger the execution of their malicious code with elevated privileges. This vulnerability aligns with CWE-78 and CWE-20, which respectively address improper neutralization of special elements used in OS commands and improper input validation. The attack vector can be classified under the MITRE ATT&CK framework as privilege escalation through environment variable manipulation, specifically targeting the 'Modify Existing Service' and 'Exploitation for Privilege Escalation' techniques.
The mitigation strategies for this vulnerability require multiple approaches to address both the immediate security issue and prevent similar problems in the future. The most direct solution involves modifying the aserver program to explicitly specify full paths to all system commands it executes, rather than relying on PATH resolution. This approach prevents attackers from substituting legitimate system binaries with malicious versions. Additionally, system administrators should implement proper file permissions and access controls to limit who can modify system PATH variables or create executables in directories that might be included in the PATH. The vulnerability also highlights the importance of secure coding practices, particularly in Unix environments where command execution is common, and emphasizes the need for input validation and environment variable sanitization. System hardening measures including regular security audits, monitoring for unauthorized PATH modifications, and implementing privilege separation techniques can further reduce the attack surface and prevent exploitation of similar vulnerabilities in other system components.