CVE-2009-3572 in OpenBSD
Summary
by MITRE
OpenBSD 4.4, 4.5, and 4.6, when running on an i386 kernel, does not properly handle XMM exceptions, which allows local users to cause a denial of service (kernel panic) via unspecified vectors.
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Analysis
by VulDB Data Team • 01/22/2019
The vulnerability identified as CVE-2009-3572 represents a critical kernel-level flaw affecting OpenBSD versions 4.4, 4.5, and 4.6 when operating on i386 architecture systems. This issue stems from inadequate handling of XMM (Extended MMX) exceptions within the kernel's exception processing mechanisms. The flaw specifically manifests when the system encounters certain XMM register operations that trigger exception conditions, leading to improper kernel state management and subsequent system instability.
The technical root cause of this vulnerability lies in the kernel's failure to properly manage XMM exception contexts during processor exception handling routines. XMM registers are 128-bit vector processing units that support multimedia instructions and floating-point operations, commonly utilized in modern x86 processors. When an XMM exception occurs during kernel execution, the system should properly transition to exception handling code that can safely manage the processor state and maintain system integrity. However, the OpenBSD kernel implementation contains a flaw in its exception dispatch logic that fails to correctly process these specific exception conditions, resulting in kernel panic conditions.
From an operational impact perspective, this vulnerability presents a significant denial of service risk for systems running affected OpenBSD versions. Local users possessing basic system access can exploit this flaw to trigger kernel panics, effectively causing system crashes and forcing complete system restarts. The vulnerability's local nature means that any user with access to the system can potentially exploit it without requiring special privileges or network access, making it particularly concerning for multi-user environments where privilege separation may be insufficient. The kernel panic conditions caused by this vulnerability can result in complete system downtime, data loss, and service disruption that may require manual intervention to restore normal operations.
This vulnerability maps to CWE-248, which describes "Uncaught Exception" in software systems, specifically within kernel contexts where proper exception handling mechanisms fail to account for all possible processor states and conditions. The flaw also relates to ATT&CK technique T1499.004, which covers "Endpoint Denial of Service" through kernel-level exploits that cause system crashes and resource exhaustion. The i386 architecture-specific nature of this vulnerability indicates that systems using x86 processors with XMM support are at risk, while newer architectures with different exception handling models may be immune to similar issues. Organizations should prioritize patching affected systems and implementing monitoring for kernel panic events that may indicate exploitation attempts, as the vulnerability can be leveraged for persistent service disruption attacks.
Mitigation strategies for this vulnerability require immediate system updates to patched OpenBSD versions that properly handle XMM exceptions. System administrators should implement comprehensive patch management procedures to ensure all affected systems receive the necessary kernel updates. Additionally, monitoring systems should be configured to detect kernel panic events and alert administrators to potential exploitation attempts. While no specific workarounds exist for this particular kernel-level flaw, organizations can implement additional security controls such as restricting local user access where possible and maintaining robust backup and recovery procedures to minimize the impact of potential exploitation. The vulnerability demonstrates the critical importance of proper exception handling in kernel code and highlights the need for thorough testing of processor-specific features in operating system implementations.