CVE-2007-0394 in HP-UX
Summary
by MITRE
HP HP-UX B11.11 does not properly verify the status of file descriptors before setuid execution, which allows local users to gain privileges by closing file descriptor 0, 1, or 2 and then invoking a setuid program, a variant of CVE-2002-0572.
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Analysis
by VulDB Data Team • 08/17/2018
The vulnerability described in CVE-2007-0394 represents a critical privilege escalation flaw within HP-UX B11.11 operating systems that stems from improper file descriptor verification during setuid execution processes. This issue specifically targets the operating system's handling of standard input output and error streams, which are represented by file descriptors 0, 1, and 2 respectively. The flaw enables local attackers to manipulate these fundamental system resources to bypass security controls designed to prevent unauthorized privilege elevation.
This vulnerability operates through a well-established exploitation technique that leverages the inherent behavior of setuid programs and their interaction with file descriptors. When a setuid program executes, it typically inherits the file descriptor table from its parent process, which includes the standard streams that are normally associated with the controlling terminal. The vulnerability arises because the system fails to properly validate whether these file descriptors are properly initialized or have been closed by the executing process. This oversight creates an exploitable condition where an attacker can close the standard file descriptors and then invoke a setuid program, effectively allowing the program to execute without proper terminal association.
The operational impact of this vulnerability extends beyond simple privilege escalation as it represents a fundamental flaw in the Unix security model's implementation. When file descriptors 0, 1, or 2 are closed before setuid execution, the setuid program may inadvertently inherit a state where it believes it is running in a terminal environment when it is not. This misidentification can lead to the program executing with elevated privileges while operating in an untrusted context. The vulnerability is particularly concerning because it affects the core system functionality that governs how programs interact with standard input output and error streams, which are essential components of system security.
This issue is classified under CWE-256, which addresses the problem of inadequate input validation and improper handling of system resources during privilege transitions. The vulnerability aligns with ATT&CK technique T1068, which covers privilege escalation through exploitation of system-level vulnerabilities. The flaw demonstrates how seemingly minor implementation details in system call handling can create significant security weaknesses. The exploitation method follows patterns similar to CVE-2002-0572, indicating a persistent class of vulnerabilities in Unix-like systems where file descriptor management during privilege transitions is not properly enforced.
Mitigation strategies for this vulnerability require both immediate system patches and careful operational procedures. System administrators must ensure that all HP-UX systems are updated with the appropriate security patches provided by HP to address this specific flaw. Additionally, implementing proper file descriptor management practices during program execution can help prevent exploitation. Organizations should also consider monitoring for suspicious patterns of file descriptor closure before setuid operations, as well as implementing privilege separation techniques that minimize the exposure of setuid programs to potentially compromised file descriptor states. The vulnerability underscores the importance of rigorous security testing for system call interfaces and proper validation of resource states during critical privilege transitions, particularly in environments where setuid programs are commonly used.