CVE-2026-53193
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk4th percentile — higher than 4% of all known CVEs
Summary
In the Linux kernel, a use-after-free vulnerability was found in the ALSA timer subsystem. When a timer object is freed via snd_timer_free, slave timer instances still point to the freed object, leading to potential memory corruption. The bug is easily triggered with the new userspace-driven timers (CONFIG_SND_UTIMER).
Risk Assessment
An attacker could exploit this vulnerability for privilege escalation or denial of service (DoS) by deliberately opening and closing timer files while other applications still access the timer.
Recommendation
Immediately update the Linux kernel to a version containing the fix that forcibly closes all timer instances (including slave ones) when the timer object is freed.
Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: ALSA: timer: Forcibly close timer instances at closing When snd_timer object is freed via snd_timer_free() and still pending snd_timer_instance objects are assigned to the timer object, it tries to unlink all instances and just set NULL to each ti->timer, then releases the resources immediately. The problem is, however, when there are slave timer instances that are associated with a master instance linked to this timer: namely, those slave instances still point to the freed timer object although the master instance is unlinked, which may lead to user-after-free. The bug can be easily triggered particularly when a new userspace-driven timers (CONFIG_SND_UTIMER) is involved, since it can create and delete the timer object via a simple file open/close, while the other applications may keep accessing to that timer. This patch is an attempt to paper over the problem above: now instead of just unlinking, call snd_timer_close[_locked]() forcibly for each pending timer instance, so that all assigned slave timer instances are properly detached, too. Since snd_timer_close() might be called later by the driver that created that instance, the check of SNDRV_TIMER_IFLG_DEAD is added at the beginning, too.