CVE-2026-43437 ALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain()
A use-after-free in the Linux kernel ALSA PCM driver allows local attackers to execute arbitrary code or escalate privileges via a race condition during stream draining.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-43437?
CVE-2026-43437 is a high-severity use after free vulnerability in Linux kernel, published on 8 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
ALSA: pcm: fix use-after-free on linked stream runtime in snd_pcm_drain()
In the drain loop, the local variable 'runtime' is reassigned to a linked stream's runtime (runtime = s->runtime at line 2157). After releasing the stream lock at line 2169, the code accesses runtime->no_period_wakeup, runtime->rate, and runtime->buffer_size (lines 2170-2178) — all referencing the linked stream's runtime without any lock or refcount protecting its lifetime.
A concurrent close() on the linked stream's fd triggers snd_pcm_release_substream() → snd_pcm_drop() → pcm_release_private() → snd_pcm_unlink() → snd_pcm_detach_substream() → kfree(runtime). No synchronization prevents kfree(runtime) from completing while the drain path dereferences the stale pointer.
Fix by caching the needed runtime fields (no_period_wakeup, rate, buffer_size) into local variables while still holding the stream lock, and using the cached values after the lock is released.
Weakness: CWE-416
Which versions are affected by CVE-2026-43437?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43437?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-43437 being exploited?
There is no known exploitation of CVE-2026-43437 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43437, DEBIAN-CVE-2026-43437, GHSA-5cw4-rfp6-xjfx, ROOT-OS-DEBIAN-11-CVE-2026-43437, ROOT-OS-UBUNTU-2204-CVE-2026-43437, ROOT-OS-UBUNTU-2404-CVE-2026-43437 and 1 more.