CVE-2002-1500 in NetBSD
Summary
by MITRE
Buffer overflow in (1) mrinfo, (2) mtrace, and (3) pppd in NetBSD 1.4.x through 1.6 allows local users to gain privileges by executing the programs after filling the file descriptor tables, which produces file descriptors larger than FD_SETSIZE, which are not checked by FD_SET().
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Analysis
by VulDB Data Team • 07/01/2024
The vulnerability described in CVE-2002-1500 represents a critical buffer overflow issue affecting multiple network utilities in NetBSD versions 1.4.x through 1.6. This flaw specifically impacts mrinfo, mtrace, and pppd programs which are integral components of the NetBSD operating system's networking infrastructure. The vulnerability stems from inadequate bounds checking in file descriptor handling mechanisms, creating a pathway for privilege escalation attacks. The affected programs operate with elevated privileges due to their system-level functions, making this vulnerability particularly dangerous as it allows local attackers to exploit the system's networking capabilities to gain unauthorized administrative access.
The technical implementation of this vulnerability relies on the exploitation of file descriptor table limitations within the operating system's select() system call implementation. When these programs execute with sufficient file descriptors open, they can create file descriptor numbers that exceed the FD_SETSIZE limit, which is a fundamental constraint in Unix-like systems for the maximum number of file descriptors that can be monitored by select() and poll() system calls. The FD_SET() function fails to validate these oversized file descriptors, leading to memory corruption that can be leveraged for privilege escalation. This flaw directly relates to CWE-121, which addresses stack-based buffer overflows, and CWE-122, which covers heap-based buffer overflows, though the specific mechanism here involves file descriptor handling rather than traditional memory allocation issues.
The operational impact of this vulnerability extends beyond simple privilege escalation as it affects the core networking functionality of affected NetBSD systems. Local users who can execute these programs with sufficient file descriptor exhaustion can potentially compromise the entire system by leveraging the elevated privileges of the vulnerable applications. The exploitation requires careful preparation of file descriptor tables to exceed the FD_SETSIZE threshold, making this a sophisticated attack that demands understanding of the underlying system architecture. This vulnerability particularly affects systems running older NetBSD versions where the file descriptor handling mechanisms were not properly hardened against such edge cases, creating persistent security risks for organizations maintaining legacy systems.
Mitigation strategies for CVE-2002-1500 require immediate system updates to newer NetBSD releases where the vulnerability has been addressed through proper bounds checking and file descriptor validation. System administrators should implement process monitoring to detect abnormal file descriptor usage patterns that might indicate exploitation attempts. The recommended approach includes upgrading to NetBSD 1.6.1 or later versions where the underlying file descriptor handling has been corrected. Additionally, implementing proper privilege separation and limiting the number of concurrent file descriptors available to these programs can reduce the attack surface. Organizations should also consider implementing automated monitoring solutions that can detect when file descriptor limits are approaching critical thresholds, as outlined in the ATT&CK framework's privilege escalation techniques. The vulnerability demonstrates the importance of proper input validation and boundary checking in system-level programs, particularly those operating with elevated privileges, aligning with security best practices outlined in the Common Weakness Enumeration standards.