CVE-2016-6787 in Linux
Summary
by MITRE
kernel/events/core.c in the performance subsystem in the Linux kernel before 4.0 mismanages locks during certain migrations, which allows local users to gain privileges via a crafted application, aka Android internal bug 31095224.
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Analysis
by VulDB Data Team • 10/12/2022
The vulnerability identified as CVE-2016-6787 resides within the Linux kernel's performance subsystem, specifically in the kernel/events/core.c file. This issue represents a critical privilege escalation flaw that affects Linux kernel versions prior to 4.0. The vulnerability stems from improper lock management during thread migration operations within the performance monitoring framework, creating a race condition that malicious local users can exploit to elevate their privileges from standard user level to root access. The flaw was particularly significant as it was also tracked as Android internal bug 31095224, indicating its impact across mobile and embedded Linux systems.
The technical implementation of this vulnerability involves the performance subsystem's handling of locks when threads are migrated between different CPU cores during performance event monitoring. During these migration operations, the kernel fails to properly acquire or release locks in a consistent manner, leading to a scenario where concurrent access to shared data structures can occur. This improper lock management creates a window of opportunity for malicious applications to manipulate the kernel's internal state through carefully crafted sequences of system calls. The vulnerability specifically manifests when the kernel attempts to migrate performance monitoring contexts between processors, where the locking mechanism becomes compromised due to missing synchronization points.
The operational impact of this privilege escalation vulnerability is severe and far-reaching across various Linux-based systems including servers, desktops, and mobile devices. Local attackers with minimal privileges can exploit this flaw to execute arbitrary code with kernel-level privileges, effectively compromising the entire system. The attack vector requires only local access to the system, making it particularly dangerous in multi-user environments where untrusted users might have access to system resources. Once exploited, the vulnerability allows attackers to bypass kernel security mechanisms, modify system files, install persistent backdoors, and potentially gain access to all user data on the compromised system. This makes the vulnerability particularly concerning for enterprise environments and mobile platforms where system integrity is paramount.
Mitigation strategies for CVE-2016-6787 primarily focus on upgrading to Linux kernel version 4.0 or later, where the lock management issues have been resolved through proper synchronization mechanisms. System administrators should prioritize immediate kernel updates across all affected systems, particularly those running older kernel versions. Additionally, implementing additional security controls such as restricting local user access, monitoring for suspicious privilege escalation attempts, and maintaining regular system audits can help detect potential exploitation attempts. The vulnerability aligns with CWE-362, which describes the weakness of concurrent execution using shared resources without proper synchronization, and maps to ATT&CK technique T1068, which involves local privilege escalation through kernel exploits. Organizations should also consider implementing kernel hardening measures including disabling unnecessary performance monitoring features and employing runtime integrity checking mechanisms to further reduce the attack surface.