CVE-2014-0205 in Linux
Summary
by MITRE
The futex_wait function in kernel/futex.c in the Linux kernel before 2.6.37 does not properly maintain a certain reference count during requeue operations, which allows local users to cause a denial of service (use-after-free and system crash) or possibly gain privileges via a crafted application that triggers a zero count.
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Analysis
by VulDB Data Team • 02/15/2022
The vulnerability described in CVE-2014-0205 resides within the Linux kernel's futex subsystem, specifically in the futex_wait function located in kernel/futex.c. This flaw represents a critical security issue that affects Linux kernel versions prior to 2.6.37, where the kernel fails to properly manage reference counts during futex requeue operations. The issue stems from inadequate synchronization mechanisms that govern how the kernel tracks futex objects and their associated reference counts during complex multi-threaded operations. When a futex requeue operation occurs, the kernel must maintain accurate reference counts to ensure proper memory management and prevent premature deallocation of futex structures. The improper reference count maintenance creates a race condition scenario where the kernel may attempt to free memory that is still in use or access memory that has already been freed.
The technical exploitation of this vulnerability occurs when a local attacker crafts a malicious application that triggers specific futex requeue operations in a particular sequence. During these operations, the kernel's reference counting mechanism fails to correctly decrement the reference count when futex objects are moved between different queues or requeued to different waiters. This mismanagement leads to a situation where the reference count can reach zero prematurely, causing the kernel to free a futex structure that other threads might still be accessing. The use-after-free condition manifests as either a system crash due to invalid memory access or a more severe privilege escalation scenario where the attacker can manipulate kernel memory to gain elevated privileges. The vulnerability operates at the kernel level, making it particularly dangerous as it can compromise the entire system security model.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can potentially enable privilege escalation attacks that allow local users to execute code with kernel-level privileges. This represents a significant threat to system integrity and confidentiality, as attackers can leverage the vulnerability to gain unauthorized access to sensitive system resources. The vulnerability affects systems running Linux kernel versions earlier than 2.6.37, which includes many enterprise and embedded systems that may not have received timely security updates. The use-after-free condition can lead to unpredictable system behavior, including kernel panics, system crashes, and in some cases, the ability for attackers to escalate privileges and execute arbitrary code with root-level permissions. Organizations using affected kernel versions face substantial risk, as this vulnerability can be exploited by any local user with the ability to run applications.
Mitigation strategies for CVE-2014-0205 primarily focus on kernel version upgrades to 2.6.37 or later, where the reference counting issue has been properly addressed through enhanced synchronization mechanisms. System administrators should prioritize applying the relevant security patches and updating their kernel versions to prevent exploitation. Additionally, implementing proper access controls and privilege restrictions can limit the potential impact of exploitation, although this does not eliminate the vulnerability itself. The fix implemented in kernel version 2.6.37 involves correcting the reference counting logic in the futex subsystem to ensure proper tracking of futex object lifetimes during requeue operations. This aligns with the broader principles of secure coding practices and proper resource management as outlined in common weakness enumeration standards. The vulnerability demonstrates the critical importance of proper synchronization in kernel-level programming and highlights the need for rigorous testing of concurrent access scenarios. Organizations should also consider implementing monitoring solutions to detect potential exploitation attempts and maintain comprehensive system logging to track any suspicious activities that might indicate attempted exploitation of this vulnerability.