CVE-2026-43437
Analyzed Analyzed - Analysis Complete
Use-After-Free in Linux Kernel ALSA PCM Subsystem

Publication date: 2026-05-08

Last updated on: 2026-05-21

Assigner: kernel.org

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.
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Meta Information
Published
2026-05-08
Last Modified
2026-05-21
Generated
2026-06-19
AI Q&A
2026-05-08
EPSS Evaluated
2026-06-18
NVD
CVE-2026-43437
EUVD
EUVD-2026-28743
Affected Vendors & Products
Showing 9 associated CPEs
Vendor Product Version / Range
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel 7.0
linux linux_kernel From 6.2 (inc) to 6.6.130 (exc)
linux linux_kernel From 6.13 (inc) to 6.18.19 (exc)
linux linux_kernel From 6.7 (inc) to 6.12.78 (exc)
linux linux_kernel From 6.19 (inc) to 6.19.9 (exc)
linux linux_kernel From 5.11 (inc) to 6.1.167 (exc)
linux linux_kernel From 3.0 (inc) to 5.10.253 (exc)
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Exploitability
CWE
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KEV
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CWE ID Description
CWE-416 The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
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Executive Summary

This vulnerability is a use-after-free issue in the Linux kernel's ALSA pcm component, specifically in the snd_pcm_drain() function. During the drain loop, a local variable 'runtime' is reassigned to a linked stream's runtime. After releasing the stream lock, the code accesses fields of this linked stream's runtime without any lock or reference count to protect its lifetime.

If a concurrent close() operation occurs on the linked stream's file descriptor, it can trigger a sequence of functions that eventually free the runtime memory (kfree(runtime)). Because there is no synchronization, the drain path may dereference a pointer to memory that has already been freed, leading to a use-after-free condition.

The fix involves caching the needed runtime fields into local variables while still holding the stream lock, and then using these cached values after the lock is released to avoid accessing freed memory.

Impact Analysis

This use-after-free vulnerability can lead to undefined behavior in the Linux kernel, such as system crashes, memory corruption, or potential escalation of privileges if exploited. It may cause instability or denial of service in systems using the ALSA pcm audio subsystem.

Mitigation Strategies

The vulnerability is fixed by updating the Linux kernel to a version where the ALSA pcm drain use-after-free issue is resolved.

Specifically, the fix involves caching the needed runtime fields while holding the stream lock to prevent accessing freed memory.

Therefore, the immediate mitigation step is to apply the kernel update or patch that includes this fix.

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