CVE-2002-1476 in NetBSD
Summary
by MITRE
Buffer overflow in setlocale in libc on NetBSD 1.4.x through 1.6, and possibly other operating systems, when called with the LC_ALL category, allows local attackers to execute arbitrary code via a user-controlled locale string that has more than 6 elements, which exceeds the boundaries of the new_categories category array, as exploitable through programs such as xterm and zsh.
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Analysis
by VulDB Data Team • 06/13/2018
The vulnerability described in CVE-2002-1476 represents a critical buffer overflow condition within the setlocale function of the C standard library implementation on NetBSD operating systems. This flaw affects versions 1.4.x through 1.6 and potentially other Unix-like systems that implement similar libc functions. The vulnerability stems from inadequate bounds checking when processing locale strings, specifically when the LC_ALL category is utilized. The flaw manifests when a user-controlled locale string contains more than six elements, causing the program to write beyond the allocated boundaries of the new_categories array. This buffer overflow condition creates a potential execution path for local attackers to gain arbitrary code execution privileges on the affected system.
The technical implementation of this vulnerability exploits the fundamental design flaw in how the setlocale function processes locale category specifications. When programs such as xterm and zsh invoke setlocale with LC_ALL, they pass user-supplied locale strings that are subsequently parsed and stored in the new_categories array. The array has a fixed size that cannot accommodate more than six elements, yet the parsing logic fails to validate the number of elements present in the user-controlled input string. This oversight allows attackers to craft malicious locale strings that deliberately exceed the array boundaries, causing memory corruption that can be leveraged for code execution. The vulnerability specifically targets the libc library implementation where the setlocale function is implemented, making it a system-level security issue that affects any application relying on this standard library function.
The operational impact of CVE-2002-1476 extends beyond simple privilege escalation as it provides attackers with a reliable method for arbitrary code execution on vulnerable systems. Since xterm and zsh are commonly used terminal emulators and shell programs, attackers can exploit this vulnerability through these applications, potentially gaining control over user sessions or system processes. The local nature of this attack means that an attacker must already have access to the system, but the privilege escalation aspect allows for more significant system compromise. This vulnerability aligns with CWE-121, which describes stack-based buffer overflow conditions, and demonstrates how improper input validation can lead to memory corruption. The attack vector is particularly concerning because it can be triggered through common user applications, making the exploitation relatively straightforward and widespread across affected systems.
Mitigation strategies for this vulnerability involve both immediate patching and system hardening measures. The primary solution requires updating to patched versions of NetBSD that address the buffer overflow in the setlocale function, with the vulnerability being resolved through proper bounds checking and input validation. System administrators should also consider implementing application sandboxing for programs that invoke setlocale with user-supplied data, particularly in environments where untrusted input may be processed. Additionally, monitoring for suspicious locale string patterns and implementing runtime protections such as stack canaries or address space layout randomization can help detect or prevent exploitation attempts. The vulnerability demonstrates the importance of secure coding practices in system libraries and aligns with ATT&CK technique T1068, which covers exploit for privilege escalation, making it a critical consideration for system security hardening. Organizations should also review their application usage patterns to identify programs that may be vulnerable through their reliance on setlocale and ensure that all affected applications are updated to prevent exploitation through this vector.