CVE-2007-0392 in AIX
Summary
by MITRE
IBM AIX 5.3 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 • 04/11/2019
This vulnerability resides in IBM AIX 5.3 operating system where the privilege escalation occurs due to improper validation of file descriptor status during setuid execution. The flaw specifically targets the handling of standard file descriptors zero through two, which represent stdin, stdout, and stderr respectively. When these file descriptors are closed before invoking setuid programs, the system fails to properly verify their status, creating an exploitable condition that allows local users to elevate their privileges. This represents a classic case of improper privilege management where the operating system does not adequately check the integrity of file descriptor states before executing privileged operations.
The technical mechanism behind this vulnerability involves the setuid program execution flow where the system should validate that file descriptors remain in their expected state. When file descriptors 0, 1, or 2 are closed prior to setuid execution, the system's verification logic becomes bypassed, allowing malicious users to manipulate the program's execution environment. This flaw enables attackers to exploit the gap in file descriptor validation by simply closing standard input/output/error streams before executing setuid binaries. The vulnerability directly relates to CWE-276 which addresses improper file permissions and CWE-250 which covers execution with unnecessary privileges, both of which are fundamental security misconfigurations in Unix-like systems.
The operational impact of this vulnerability extends beyond simple privilege escalation as it provides attackers with a reliable method to gain elevated system access without requiring network connectivity or complex exploitation techniques. Local users can leverage this condition to execute setuid programs with root privileges, effectively bypassing the normal access controls that should prevent such privilege escalation. This vulnerability particularly affects systems running IBM AIX 5.3 where the kernel's file descriptor validation is insufficient during the setuid transition process. The exploitability is enhanced by the fact that closing standard file descriptors is a simple operation that requires no special privileges, making this a particularly dangerous flaw for system administrators to address.
Mitigation strategies for this vulnerability require immediate system updates and patches from IBM to address the specific file descriptor validation issue in AIX 5.3. System administrators should implement proper monitoring of setuid program execution and file descriptor states to detect potential exploitation attempts. The recommended approach involves applying the vendor-provided security patches that strengthen the validation of file descriptor status before setuid transitions occur. Additionally, implementing the principle of least privilege by reducing unnecessary setuid programs and monitoring file descriptor usage patterns can help minimize the attack surface. This vulnerability also highlights the importance of following ATT&CK framework tactics such as privilege escalation through exploitation of system vulnerabilities, emphasizing the need for comprehensive system hardening and regular security assessments. Organizations should conduct thorough vulnerability assessments to identify systems running affected AIX versions and implement proper access controls to prevent unauthorized users from gaining local access that could lead to exploitation of this condition.