CVE-2004-1323 in NetBSD
Summary
by MITRE
Multiple syscalls in the compat subsystem for NetBSD before 2.0 allow local users to cause a denial of service (kernel crash) via a large signal number to (1) xxx_sys_kill, (2) xxx_sys_sigaction, and possibly other translation functions.
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Analysis
by VulDB Data Team • 06/30/2019
The vulnerability described in CVE-2004-1323 represents a critical denial of service flaw within the compatibility subsystem of NetBSD operating systems prior to version 2.0. This issue affects the kernel's handling of system calls that translate signals between different architectural representations, specifically impacting the xxx_sys_kill and xxx_sys_sigaction functions along with potentially other translation mechanisms. The vulnerability stems from insufficient input validation within the compatibility layer that processes signal-related system calls, creating a scenario where malformed or excessively large signal numbers can trigger kernel crashes.
The technical implementation of this vulnerability involves the kernel's compat subsystem which provides backward compatibility for applications running on older architectures or binary formats. When local users execute system calls with signal numbers that exceed expected ranges, the kernel fails to properly validate these inputs before processing them through the compatibility translation functions. This lack of proper bounds checking allows malicious or malformed inputs to cause kernel memory corruption and subsequent system crashes. The vulnerability specifically targets the xxx_sys_kill and xxx_sys_sigaction functions, which are responsible for handling signal delivery and signal handler installation respectively, making it particularly dangerous as these are fundamental system operations.
The operational impact of this vulnerability extends beyond simple system instability, as it provides local attackers with a reliable method to induce kernel crashes without requiring elevated privileges. Since the vulnerability exists within the compatibility subsystem, it affects not only native NetBSD systems but also systems running legacy applications or binaries that require compatibility mode. The denial of service can be achieved through simple exploitation techniques that do not require complex attack vectors or root access. This makes the vulnerability particularly concerning for server environments where system availability is critical, as local users can potentially disrupt services by causing kernel panics and system reboots.
Mitigation strategies for CVE-2004-1323 primarily focus on upgrading to NetBSD version 2.0 or later, which contains the necessary patches to address the input validation issues in the compatibility subsystem. System administrators should also consider implementing additional security measures such as restricting local user access where possible, monitoring for unusual system behavior, and ensuring that compatibility mode is only enabled when absolutely necessary for specific applications. The vulnerability aligns with CWE-129, which addresses insufficient input validation, and represents a classic example of how compatibility layers in operating systems can introduce security weaknesses when not properly validated against malicious inputs.
This vulnerability demonstrates the importance of proper input validation in kernel space operations and highlights the risks associated with maintaining compatibility layers in operating systems. The flaw represents a direct violation of the principle of least privilege and input sanitization that should be applied to all kernel subsystems. From an attack perspective, the vulnerability is classified under the MITRE ATT&CK framework as a privilege escalation technique through system call manipulation, specifically targeting the kernel's signal handling mechanisms. The lack of proper bounds checking in the compatibility subsystem creates a pathway for local users to exploit kernel memory management functions, making it a significant concern for system administrators maintaining older NetBSD installations. Organizations should prioritize patching this vulnerability and implementing comprehensive monitoring solutions to detect potential exploitation attempts.