CVE-2026-53192 in Linux
Summary
by MITRE • 06/25/2026
In the Linux kernel, the following vulnerability has been resolved:
ALSA: timer: Fix UAF at snd_timer_user_params()
At releasing a timer object, e.g. when a userspace timer (CONFIG_SND_UTIMER) gets closed and snd_timer_free() is called, it tries to detach the timer instances and release the resources. However, it's still possible that other in-flight tasks are holding the timer instance where the to-be-deleted timer object is associated, and this may lead to racy accesses.
Fortunately, most of ioctls dealing with the timer instance list already have the protection with register_mutex, and this also avoids such races. But, SNDRV_TIMER_IOCTL_PARAMS isn't protected, hence the concurrent ioctl may lead to use-after-free.
This patch just adds the guard with register_mutex to protect snd_timer_user_params() for covering the code path as a quick workaround. It's no hot-path but rather a rarely issued ioctl, so the performance penalty doesn't matter.
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Analysis
by VulDB Data Team • 06/25/2026
The vulnerability identified in the Linux kernel represents a use-after-free condition affecting the Advanced Linux Sound Architecture timer subsystem, specifically within the snd_timer_user_params() function. This issue occurs during the cleanup process of timer objects when userspace applications close timer handles associated with CONFIG_SND_UTIMER functionality. The core problem emerges from race conditions that can occur between the timer object release process and concurrent operations accessing the same timer instance. When snd_timer_free() is invoked to release timer resources, it attempts to detach timer instances and clean up associated memory structures while other tasks may still be actively using these resources.
The technical flaw stems from insufficient synchronization mechanisms protecting certain ioctl operations within the timer subsystem. While most timer instance list operations already employ register_mutex protection to prevent concurrent access issues, the SNDRV_TIMER_IOCTL_PARAMS ioctl specifically lacks this safeguard. This creates a window where a concurrent ioctl operation can attempt to access memory that has already been freed by the cleanup process, resulting in use-after-free conditions. The vulnerability is particularly concerning because it can lead to arbitrary code execution or system crashes when malicious actors exploit the race condition through carefully crafted ioctl calls.
The operational impact of this vulnerability extends beyond simple system instability to potential security compromise. Attackers could leverage this race condition to execute arbitrary code within kernel space, potentially escalating privileges or gaining full system control. The vulnerability affects systems running Linux kernels with ALSA timer support and userspace applications utilizing the snd_utimer functionality. Since the affected ioctl operation is not part of high-frequency code paths, the performance impact of implementing the fix through register_mutex protection is minimal, making it a practical defensive measure.
This vulnerability aligns with CWE-416, Use After Free, which is classified as a critical security weakness in software systems where memory is accessed after being freed. The issue also relates to ATT&CK technique T1068, Exploitation for Privilege Escalation, as the use-after-free condition can be exploited to gain elevated privileges within the kernel space. The fix implemented represents a defensive approach that adds register_mutex protection around snd_timer_user_params(), effectively serializing access to prevent concurrent operations during timer object cleanup. This mitigation strategy aligns with standard security practices for addressing race conditions in kernel subsystems, ensuring proper synchronization between resource allocation and deallocation operations while maintaining system stability and preventing potential exploitation by malicious actors.