CVE-2026-53192: Linux Kernel Use-After-Free Vulnerability

CVE-2026-53192 Overview

CVE-2026-53192 is a use-after-free (UAF) vulnerability in the Linux kernel's Advanced Linux Sound Architecture (ALSA) timer subsystem. The flaw resides in snd_timer_user_params() and is triggered by concurrent ioctl operations on userspace timer objects (CONFIG_SND_UTIMER). When a timer is released through snd_timer_free(), in-flight tasks may still hold references to the timer instance, creating a race condition that leads to use-after-free memory access.

Most timer ioctls are serialized by register_mutex, but SNDRV_TIMER_IOCTL_PARAMS lacked this protection. The upstream fix adds a register_mutex guard around snd_timer_user_params().

Critical Impact
Local attackers with access to ALSA timer devices can trigger a kernel use-after-free condition through concurrent ioctl calls, potentially leading to memory corruption or local privilege escalation.

Affected Products

Linux kernel builds with CONFIG_SND_UTIMER enabled
Multiple stable kernel branches referenced in the upstream patch set
Distributions shipping vulnerable Linux kernel versions prior to the fix

Discovery Timeline

2026-06-25 - CVE-2026-53192 published to NVD
2026-06-25 - Last updated in NVD database

Technical Details for CVE-2026-53192

Vulnerability Analysis

The vulnerability is a classic kernel use-after-free triggered by a race between timer release and ioctl-driven parameter updates. When userspace closes a CONFIG_SND_UTIMER file descriptor, snd_timer_free() detaches timer instances and frees associated resources. However, other threads may simultaneously execute the SNDRV_TIMER_IOCTL_PARAMS ioctl, which calls snd_timer_user_params() while holding a reference to the soon-to-be-freed timer instance.

Because snd_timer_user_params() was not guarded by register_mutex, the function could operate on a timer instance after its backing object had been released. The result is a dangling pointer dereference inside kernel context, which an attacker can exploit to corrupt kernel memory.

Root Cause

The root cause is missing synchronization on a rarely-issued ioctl path. The ALSA timer code uses register_mutex to serialize most operations that traverse the timer instance list, preventing teardown races. The SNDRV_TIMER_IOCTL_PARAMS handler was omitted from this protection scheme, leaving a narrow but reachable window where the timer object could be freed while the params ioctl was still executing.

Attack Vector

Exploitation requires local access to an ALSA timer character device, typically /dev/snd/timer. An attacker opens a userspace timer, then races two threads: one closes the file descriptor to trigger snd_timer_free(), while another issues SNDRV_TIMER_IOCTL_PARAMS repeatedly. Winning the race produces a use-after-free that an attacker can shape via kernel heap manipulation to achieve memory corruption.

No verified public exploitation code is available for this issue. Technical details of the fix are available in the upstream patches, including Kernel Patch 053a401b and Kernel Patch 117743d.

Detection Methods for CVE-2026-53192

Indicators of Compromise

Kernel oops or panic logs referencing snd_timer_user_params, snd_timer_free, or ALSA timer symbols in the call stack
KASAN reports flagging use-after-free in the sound/core/timer.c code path
Unexpected process crashes or kernel module instability on hosts exposing /dev/snd/timer

Detection Strategies

Inventory running kernel versions across Linux fleets and compare against patched stable branches referenced in the upstream commits
Enable KASAN on test and pre-production kernels to surface UAF conditions in ALSA timer handling during fuzzing or regression runs
Monitor auditd and syscall telemetry for unusual volumes of ioctl calls against /dev/snd/timer from unprivileged processes

Monitoring Recommendations

Centralize kernel ring buffer and dmesg output to a SIEM and alert on oops/BUG entries containing ALSA timer symbols
Track process behavior that opens ALSA device nodes and rapidly issues ioctl operations from multiple threads
Correlate kernel crash events with the executing user and process ancestry to identify potential exploitation attempts

How to Mitigate CVE-2026-53192

Immediate Actions Required

Apply the upstream Linux kernel patch series that adds register_mutex protection around snd_timer_user_params()
Update to the patched stable kernel release provided by your Linux distribution as soon as it becomes available
Restrict access to /dev/snd/timer to trusted users where audio timer functionality is not required for all accounts

Patch Information

The fix has been merged across multiple stable kernel branches. Refer to the upstream commits for the exact code change and backport targets:

Workarounds

Disable the userspace timer feature by building kernels without CONFIG_SND_UTIMER where audio timer ioctls are not required
Tighten permissions on /dev/snd/timer so only members of trusted groups can issue timer ioctls
Unload the snd_timer module on systems that do not require ALSA timer functionality

bash

# Restrict access to the ALSA timer device
sudo chgrp audio /dev/snd/timer
sudo chmod 0660 /dev/snd/timer

# Verify the installed kernel version against patched releases
uname -r

# Optionally prevent the snd_timer module from loading where unused
echo "blacklist snd_timer" | sudo tee /etc/modprobe.d/blacklist-snd-timer.conf