CVE-2016-2069 in Linux
Summary
by MITRE
Race condition in arch/x86/mm/tlb.c in the Linux kernel before 4.4.1 allows local users to gain privileges by triggering access to a paging structure by a different CPU.
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Analysis
by VulDB Data Team • 07/27/2022
The vulnerability identified as CVE-2016-2069 represents a critical race condition within the Linux kernel's memory management subsystem, specifically in the translation lookaside buffer implementation located at arch/x86/mm/tlb.c. This flaw exists in kernel versions prior to 4.4.1 and fundamentally undermines the integrity of the kernel's virtual memory management system by creating a window where concurrent CPU operations can lead to unpredictable behavior. The race condition occurs when multiple processors attempt to access and modify paging structures simultaneously, creating a scenario where one CPU's operations can interfere with another's during the critical moments of page table manipulation.
The technical exploitation of this vulnerability leverages the inherent timing issues in how the kernel handles memory translation and page table updates across multiple CPU cores. When a CPU attempts to access a paging structure while another CPU is modifying it, the system can end up in an inconsistent state where page table entries are either partially updated or corrupted. This creates opportunities for privilege escalation because malicious code running in user space can manipulate the timing of memory operations to force the kernel into executing code with elevated privileges. The vulnerability specifically targets the TLB (Translation Lookaside Buffer) management code which is responsible for caching virtual-to-physical address translations and maintaining consistency across the system's memory management units.
The operational impact of this vulnerability extends beyond simple privilege escalation to potentially enable complete system compromise. An attacker with local access can exploit this race condition to execute arbitrary code with kernel-level privileges, effectively bypassing all user-mode security controls and access restrictions. This allows for persistent system compromise, data exfiltration, and the installation of rootkits or other malicious software that can operate below the detection capabilities of standard security tools. The vulnerability's local nature means that any user with access to the system can potentially exploit it, making it particularly dangerous in multi-user environments or systems where user access is not strictly controlled.
Mitigation strategies for CVE-2016-2069 primarily focus on kernel version updates and system hardening measures. The most effective solution involves upgrading to Linux kernel version 4.4.1 or later, where the race condition has been addressed through improved synchronization mechanisms and more robust handling of concurrent page table modifications. Additionally, system administrators should implement strict access controls and monitor for unusual memory access patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-362, which describes race conditions in concurrent programming, and maps to ATT&CK technique T1068, which covers local privilege escalation through kernel exploits. Organizations should also consider implementing kernel lockdown mechanisms and using security modules like SELinux or AppArmor to provide additional layers of protection against exploitation attempts.