CVE-2012-2373 in Linux
Summary
by MITRE
The Linux kernel before 3.4.5 on the x86 platform, when Physical Address Extension (PAE) is enabled, does not properly use the Page Middle Directory (PMD), which allows local users to cause a denial of service (panic) via a crafted application that triggers a race condition.
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Analysis
by VulDB Data Team • 03/25/2021
The vulnerability identified as CVE-2012-2373 represents a critical flaw in the Linux kernel's memory management subsystem that specifically affects systems utilizing the x86 platform with Physical Address Extension enabled. This issue exists within kernel versions prior to 3.4.5 and demonstrates how improper handling of memory page structures can lead to system instability. The flaw manifests when the kernel fails to correctly manage the Page Middle Directory (PMD) structure, which serves as an intermediate level in the page table hierarchy that maps virtual addresses to physical addresses. The vulnerability is particularly concerning because it operates at the kernel level, allowing local attackers with minimal privileges to potentially disrupt system operations through carefully crafted applications.
The technical root cause of this vulnerability stems from a race condition that occurs within the kernel's memory management code when PAE is enabled. When PAE is active, the kernel must manage multiple levels of page tables to handle extended physical addresses beyond the standard 32-bit limit. The flaw occurs in how the kernel handles the transition and manipulation of page middle directory entries during memory allocation and deallocation operations. This race condition allows malicious applications to exploit timing dependencies in the kernel's page table management routines, specifically when the kernel attempts to update or access PMD entries. The improper use of PMD structures means that concurrent memory operations can result in inconsistent page table states, leading to kernel panic conditions.
The operational impact of this vulnerability extends beyond simple denial of service, as it can potentially compromise system stability and availability in production environments. Local users who can execute crafted applications can trigger the race condition repeatedly, causing the kernel to panic and restart the system. This makes the vulnerability particularly dangerous in server environments where system uptime is critical and in embedded systems where automatic restarts may not be desirable. The vulnerability affects systems running Linux kernel versions up to 3.4.4, making it a significant concern for organizations that have not yet upgraded their kernel versions. The local nature of the exploit means that any user with basic execution privileges can potentially trigger the condition, making it a widespread risk across various deployment scenarios.
Mitigation strategies for CVE-2012-2373 primarily focus on kernel version upgrades to 3.4.5 or later, which contain the necessary patches to address the race condition in PMD handling. Organizations should prioritize updating their kernel versions as a critical security measure, especially in environments where untrusted users might have access to system resources. Additionally, system administrators can implement kernel lockdown mechanisms and disable PAE if it is not required for specific hardware configurations. The vulnerability aligns with CWE-362, which describes race conditions in software systems, and corresponds to ATT&CK technique T1499.004 for Denial of Service through kernel exploitation. Regular security audits should include checks for outdated kernel versions, and system monitoring should be implemented to detect potential exploitation attempts. The patch for this vulnerability specifically addresses the synchronization mechanisms used in memory management operations to prevent the race condition that leads to kernel panics.