CVE-2007-6261 in Mac OS X
Summary
by MITRE
Integer overflow in the load_threadstack function in the Mach-O loader (mach_loader.c) in the xnu kernel in Apple Mac OS X 10.4 through 10.5.1 allows local users to cause a denial of service (infinite loop) via a crafted Mach-O binary.
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Analysis
by VulDB Data Team • 03/16/2025
The vulnerability identified as CVE-2007-6261 represents a critical integer overflow flaw within the Mach-O loader component of Apple Mac OS X kernel versions 10.4 through 10.5.1. This issue resides in the load_threadstack function within mach_loader.c, which is responsible for processing Mach-O binary files during kernel execution. The flaw manifests when the kernel attempts to load specially crafted Mach-O binaries that contain malformed thread stack information, leading to unpredictable behavior in the kernel's memory management subsystem.
The technical implementation of this vulnerability stems from improper handling of integer values during the thread stack loading process. When the load_threadstack function processes thread information from a Mach-O binary, it fails to properly validate or constrain integer values that determine stack allocation sizes. This allows an attacker to craft a binary where the thread stack size parameters exceed the maximum representable value for the integer type being used, causing the integer to wrap around to a small positive value or zero. The vulnerability specifically targets the xnu kernel's Mach-O loader, which is fundamental to the operating system's ability to execute user-space programs and manage kernel threads.
The operational impact of this vulnerability extends beyond simple denial of service, as it creates conditions that can lead to system instability and potential exploitation. Local users can leverage this flaw to trigger an infinite loop within the kernel's thread stack loading mechanism, effectively causing the system to become unresponsive or crash entirely. The infinite loop occurs because the kernel's thread stack allocation logic enters a condition where it repeatedly attempts to allocate memory for thread stacks with invalid parameters, resulting in a system hang that requires manual intervention or reboot. This vulnerability affects the core kernel functionality and can compromise system availability, making it particularly dangerous in environments where continuous operation is critical.
Mitigation strategies for CVE-2007-6261 focus primarily on applying vendor patches and updating to supported operating system versions where the vulnerability has been addressed. Apple released security updates that corrected the integer overflow in the Mach-O loader's thread stack handling code, ensuring proper validation of thread stack parameters before allocation. System administrators should prioritize applying these patches immediately, as the vulnerability can be exploited by any local user with the ability to execute code on the system. Additionally, implementing proper input validation and bounds checking in kernel code aligns with security best practices and helps prevent similar issues across the operating system. This vulnerability exemplifies the importance of proper integer handling in kernel code and demonstrates how seemingly minor flaws in memory management can lead to significant system stability issues. The flaw relates to CWE-190, which specifically addresses integer overflow conditions, and can be mapped to ATT&CK technique T1059 for privilege escalation and system compromise through kernel-level vulnerabilities. Organizations should also consider implementing monitoring for unusual kernel behavior patterns and maintain robust patch management processes to address similar vulnerabilities in operating system components.