CVE-2007-4573 in Linux
Summary
by MITRE
The IA32 system call emulation functionality in Linux kernel 2.4.x and 2.6.x before 2.6.22.7, when running on the x86_64 architecture, does not zero extend the eax register after the 32bit entry path to ptrace is used, which might allow local users to gain privileges by triggering an out-of-bounds access to the system call table using the %RAX register.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability described in CVE-2007-4573 represents a critical privilege escalation flaw within the Linux kernel's system call emulation layer on x86_64 architectures. This issue affects kernel versions 2.4.x through 2.6.22.6, creating a pathway for local attackers to exploit improper register handling during 32-bit system call execution. The flaw specifically manifests when the ptrace functionality is utilized through the 32-bit entry path, where the kernel fails to properly zero-extend the eax register before transitioning to the 64-bit execution context. This omission creates a condition where the upper 32 bits of the RAX register retain their original values from the 32-bit execution environment, potentially leading to unintended memory access patterns.
The technical exploitation of this vulnerability stems from the improper handling of register state during system call transitions in the IA32 emulation layer. When a 32-bit process makes a system call through ptrace on a 64-bit kernel, the kernel's emulation code does not correctly zero-extend the 32-bit result stored in eax to the full 64-bit RAX register. This incomplete register management creates a scenario where the upper 32 bits of RAX contain arbitrary data from previous operations, which can subsequently influence the indexing of system call table lookups. The vulnerability is classified under CWE-125 as an out-of-bounds read condition, where the improper register state leads to invalid memory access patterns that can be manipulated to access privileged system resources.
The operational impact of this vulnerability extends beyond simple privilege escalation to encompass potential system compromise and data integrity breaches. Local attackers can leverage this flaw to gain elevated privileges within the kernel context, potentially allowing them to execute arbitrary code with root-level permissions. The attack vector requires local system access and the ability to execute ptrace operations, making it particularly concerning for environments where untrusted users have access to system resources. This vulnerability directly maps to ATT&CK technique T1068, which covers privilege escalation through local system exploitation, and specifically targets the kernel-level privilege escalation pathways that are fundamental to system security.
Mitigation strategies for CVE-2007-4573 require immediate kernel version updates to 2.6.22.7 or later, which contain the necessary patches to properly zero-extend registers during the system call transition process. System administrators should also implement comprehensive monitoring for ptrace usage and anomalous system call patterns that might indicate exploitation attempts. Additional defensive measures include restricting local user access where possible, implementing proper privilege separation, and maintaining up-to-date security patches across all kernel versions. The vulnerability demonstrates the critical importance of proper register state management in kernel-level code and highlights the need for thorough testing of system call emulation pathways, particularly in mixed 32-bit and 64-bit execution environments. Organizations should conduct vulnerability assessments to identify systems running affected kernel versions and prioritize patch deployment to prevent exploitation of this privilege escalation vector.