CVE-2025-39997
Published Oct 15, 2025
Modified Apr 15, 2026
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.
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References
Other References
https://git.kernel.org/stable/c/353d8c715cc951a980728133c9dd64ca5a0a186c
https://git.kernel.org/stable/c/647d6b8d22be12842fde6ed0c56859ebc615f21e
https://git.kernel.org/stable/c/9f2c0ac1423d5f267e7f1d1940780fc764b0fee3
https://git.kernel.org/stable/c/af600e7f5526d16146b3ae99f6ad57bfea79ca33
https://git.kernel.org/stable/c/dc4874366cf6cf4a31d8fa4b7f0e2a5b2d7647ba
Frequently Asked Questions
What is CVE-2025-39997? +
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.
How do I check if I'm vulnerable to CVE-2025-39997? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.