CVE-2017-10661 in Linux
Summary
by MITRE
Race condition in fs/timerfd.c in the Linux kernel before 4.10.15 allows local users to gain privileges or cause a denial of service (list corruption or use-after-free) via simultaneous file-descriptor operations that leverage improper might_cancel queueing.
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Analysis
by VulDB Data Team • 12/27/2024
The vulnerability identified as CVE-2017-10661 represents a critical race condition within the Linux kernel's timerfd implementation located in fs/timerfd.c. This flaw affects kernel versions prior to 4.10.15 and exposes systems to both privilege escalation and denial of service attacks through improper handling of file descriptor operations. The race condition occurs when multiple simultaneous operations target the same timerfd file descriptor, creating a scenario where the kernel's internal data structures become corrupted or improperly managed.
The technical root cause stems from inadequate synchronization mechanisms within the timerfd subsystem, specifically in how the kernel manages the might_cancel queue during concurrent file descriptor operations. When multiple processes or threads attempt to manipulate the same timerfd descriptor simultaneously, the kernel fails to properly coordinate these operations, leading to a race condition that can result in memory corruption. This improper queueing mechanism allows for list corruption and potential use-after-free conditions, where freed memory locations are accessed by subsequent operations, creating exploitable scenarios.
From an operational perspective, this vulnerability poses significant risks to system integrity and availability. Local attackers can exploit this race condition to escalate privileges by manipulating the kernel's internal data structures, potentially gaining unauthorized access to system resources. The denial of service aspect creates additional attack vectors where legitimate system operations may be disrupted through list corruption or memory management issues that cause kernel panics or system instability. The vulnerability's impact is particularly concerning in multi-user environments where multiple processes might interact with timerfd operations simultaneously.
The flaw aligns with CWE-362, which identifies race conditions as a critical weakness in concurrent systems, and maps to ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' through kernel vulnerabilities. Additionally, the vulnerability demonstrates characteristics of T1499, 'Endpoint Denial of Service', through its potential to cause system instability and resource exhaustion. Organizations should prioritize patching affected systems to kernel version 4.10.15 or later, as this update addresses the synchronization issues within the timerfd implementation and resolves the improper queueing mechanisms that enable the race condition.
Mitigation strategies include implementing immediate kernel updates, monitoring system logs for unusual timerfd operations, and applying additional security controls to limit local user privileges. System administrators should also consider implementing process isolation and monitoring for concurrent file descriptor operations that might trigger the race condition. The vulnerability highlights the importance of thorough testing and validation of concurrent kernel subsystems, particularly those handling inter-process communication mechanisms like timerfd, which are fundamental to system stability and security.