CVE-2025-39997 ALSA: usb-audio: fix race condition to UAF in snd_usbmidi_free
A race condition in the Linux kernel's USB audio driver allows local attackers to trigger a use-after-free, potentially leading to code execution or privilege escalation.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-39997?
CVE-2025-39997 is an use after free vulnerability in Linux, published on 15 Oct 2025. 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: 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.
Which versions are affected by CVE-2025-39997?
How do I fix CVE-2025-39997?
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-2025-39997 being exploited?
There is no known exploitation of CVE-2025-39997 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-39997, DEBIAN-CVE-2025-39997, GHSA-xc3r-7j5x-74w4, UBUNTU-CVE-2025-39997.