CVE-2026-53192

What it actually does

This is a race-condition use-after-free vulnerability in the Linux kernel ALSA timer subsystem. When a userspace ALSA timer object is being released, another task can concurrently issue the SNDRV_TIMER_IOCTL_PARAMS ioctl against a timer instance that still references the object being freed. Because snd_timer_user_params() was not protected by the same register_mutex locking used by most other timer ioctls, the kernel can access freed memory. Depending on kernel build options, allocator state, and exploit reliability, this may cause a kernel crash, memory corruption, information disclosure, or potentially local privilege escalation.

Why it matters to the business

The primary risk is to Linux systems that expose ALSA timer functionality to local users or sandboxed workloads. Successful exploitation could disrupt systems through kernel crashes or, in a more advanced exploit, allow a local attacker to gain elevated privileges and take control of the host. The issue is not currently listed in CISA KEV, is not known to be used in ransomware campaigns, and has a low EPSS score, so broad internet-scale exploitation is unlikely; however, kernel local privilege escalation bugs can become important when chained with an initial foothold.

How an attack unfolds

An attacker first needs local code execution on a vulnerable Linux system with the ALSA userspace timer interface enabled. They open the ALSA timer device, create or use a userspace timer instance, and then deliberately race two operations: one path closes or frees the timer object, while another concurrently sends the SNDRV_TIMER_IOCTL_PARAMS ioctl. Because the ioctl handler lacked the necessary mutex protection, it may dereference a timer object that has already been freed. A simple exploit may only trigger a denial of service by crashing the kernel. A more sophisticated exploit would attempt to shape kernel heap memory so that the freed object is replaced with attacker-controlled data, turning the use-after-free into controlled memory corruption and possible privilege escalation.

How to fix it

Upgrade to a Linux kernel version from the applicable distribution or vendor that includes the ALSA timer fix adding register_mutex protection around snd_timer_user_params(). Because exact fixed package versions were not provided, use the security advisory from the Linux distribution or kernel vendor for the deployed kernel branch. If immediate patching is not possible, reduce exposure by disabling unneeded sound/ALSA functionality on servers, restricting access to /dev/snd/* device nodes, avoiding granting containers or untrusted workloads access to host sound devices, and limiting local shell access to trusted users. Standard hardening such as SELinux/AppArmor confinement, seccomp profiles restricting ioctl-heavy device access, and kernel lockdown can reduce exploitability but should not be treated as a substitute for patching.

How to confirm the fix worked

Confirm the running kernel includes the vendor fix for the ALSA timer use-after-free in snd_timer_user_params(). Validate both installed and running kernel versions, because systems may have installed a fixed kernel but still be running an older one until rebooted. Check whether ALSA timer support is present and reachable by verifying the existence and permissions of /dev/snd/timer and whether CONFIG_SND_TIMER and CONFIG_SND_UTIMER are enabled in the kernel configuration. On patched systems, regression testing should confirm normal ALSA timer operations continue to work and that concurrent close/ioctl stress tests no longer produce KASAN, KCSAN, slab, general protection fault, or kernel oops messages referencing snd_timer_user_params or snd_timer_free.

Typical attack path

1. Obtain local execution on a vulnerable Linux host, container, desktop, workstation, or server where ALSA timer functionality is available.
2. Confirm access to the ALSA timer interface, commonly through /dev/snd/timer or equivalent device nodes.
3. Open or create a userspace ALSA timer object.
4. Run concurrent threads or processes that repeatedly close/free the timer while issuing SNDRV_TIMER_IOCTL_PARAMS ioctl calls.
5. Trigger the race so snd_timer_user_params() accesses a freed timer object.
6. Cause a kernel crash or attempt heap grooming to convert the use-after-free into privilege escalation.
7. If privilege escalation succeeds, establish persistence, access sensitive data, or move laterally using the compromised host privileges.

How to detect it

This vulnerability is a local kernel race condition, so exploitation evidence is most likely to appear in host-level telemetry rather than network logs. Review kernel logs, journald, dmesg, crash dumps, audit logs, and EDR process telemetry for signs of repeated access to ALSA timer devices followed by kernel instability. Look for kernel warnings or crashes referencing snd_timer_user_params(), snd_timer_free(), ALSA timer ioctl handling, use-after-free, KASAN, slab corruption, general protection faults, or kernel oops messages. Audit logs may show unusual opens of /dev/snd/timer by non-audio processes, exploit-like binaries, fuzzers, shell scripts, or containerized workloads. Container and orchestration logs should be reviewed for workloads granted /dev/snd device access. Because public exploit maturity is currently listed as none and the CVE is not in KEV, absence of known exploit-tool indicators is expected; detection should focus on behavioral evidence and kernel crash artifacts.

• /dev/snd/timer
• SNDRV_TIMER_IOCTL_PARAMS
• snd_timer_user_params
• snd_timer_free
• ALSA: timer
• use-after-free
• KASAN: use-after-free
• BUG: KASAN
• general protection fault
• kernel BUG
• Oops:
• slab-use-after-free
• CONFIG_SND_UTIMER
• CONFIG_SND_TIMER

What your security team should do

• Inventory Linux systems where ALSA sound or timer devices are enabled, especially multi-user servers, developer workstations, VDI hosts, and container hosts that pass through /dev/snd devices.
• Prioritize patching systems that allow untrusted local users, shared shell access, desktop logins, CI workloads, or containers with access to host sound devices.
• Apply the vendor-fixed kernel and reboot to ensure the fixed kernel is running.
• Until patching is complete, remove or restrict access to /dev/snd/timer and avoid passing /dev/snd/* into containers or sandboxes used by untrusted code.
• Monitor kernel logs for crashes, KASAN reports, slab corruption, or oops traces involving ALSA timer functions.
• Ensure endpoint and workload policies prevent untrusted users from compiling and running arbitrary local exploit code where possible.
• Treat any unexplained kernel crash involving snd_timer_user_params, snd_timer_free, or ALSA timer ioctl activity as suspicious and investigate for possible local exploitation attempts.