CVE-2006-5836 in Darwin kernel
Summary
by MITRE
The fpathconf syscall function in bsd/kern/kern_descrip.c in the Darwin kernel (XNU) 8.8.1 in Apple Mac OS X allows local users to cause a denial of service (kernel panic) and possibly execute arbitrary code via a file descriptor with an unrecognized file type.
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Analysis
by VulDB Data Team • 04/27/2026
The vulnerability identified as CVE-2006-5836 resides within the Darwin kernel implementation of Mac OS X version 8.8.1, specifically in the fpathconf system call function located in bsd/kern/kern_descrip.c. This flaw represents a critical security issue that affects the kernel's handling of file descriptors with unrecognized file types, creating potential pathways for both denial of service and arbitrary code execution. The vulnerability stems from inadequate validation and error handling within the kernel's file descriptor management subsystem, where the fpathconf function fails to properly process file descriptors that do not correspond to recognized file types.
The technical exploitation of this vulnerability occurs when a local attacker manipulates file descriptors to reference files of unrecognized types, triggering a kernel panic through improper memory access patterns. The flaw operates at the kernel level where the system call does not adequately validate the file type before attempting to process configuration parameters, creating a scenario where malformed file descriptors can cause the kernel to crash or behave unpredictably. This represents a classic case of improper input validation and insufficient error handling that violates fundamental security principles. The vulnerability aligns with CWE-125, which addresses out-of-bounds read conditions, and CWE-248, which covers exposure of an exception to an unexpected environment.
The operational impact of this vulnerability extends beyond simple denial of service, as it potentially enables local privilege escalation and arbitrary code execution within the kernel context. When a kernel panic occurs, the system becomes unavailable, requiring manual reboot to restore functionality, while the possibility of code execution represents a more severe threat to system integrity and confidentiality. Attackers can leverage this vulnerability to compromise the entire operating system, as kernel-level access provides complete control over system resources, user data, and network communications. The local nature of the attack means that exploitation requires only user-level access, making it particularly dangerous in multi-user environments where privilege separation is essential.
Mitigation strategies for this vulnerability should include immediate system updates to patched versions of Mac OS X, as Apple would have released security updates addressing this specific kernel flaw. System administrators should implement proper access controls and monitor for unusual file descriptor usage patterns that might indicate attempted exploitation. The vulnerability demonstrates the importance of robust kernel security practices and proper input validation, aligning with ATT&CK technique T1068 which covers local privilege escalation. Additionally, organizations should consider implementing kernel hardening measures such as kernel address space layout randomization and stack canaries to reduce the effectiveness of potential exploitation attempts. Regular security assessments and kernel integrity monitoring should be implemented to detect and prevent similar vulnerabilities from being exploited in other system components.