CVE-2025-40269 ALSA: usb-audio: Fix potential overflow of PCM transfer buffer
A buffer overflow in the Linux kernel USB audio driver allows attackers to cause denial of service or execute code via malicious USB descriptors.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-40269?
CVE-2025-40269 is a high-severity memory corruption vulnerability in Linux, published on 6 Dec 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 potential overflow of PCM transfer buffer
The PCM stream data in USB-audio driver is transferred over USB URB packet buffers, and each packet size is determined dynamically. The packet sizes are limited by some factors such as wMaxPacketSize USB descriptor. OTOH, in the current code, the actually used packet sizes are determined only by the rate and the PPS, which may be bigger than the size limit above. This results in a buffer overflow, as reported by syzbot.
Basically when the limit is smaller than the calculated packet size, it implies that something is wrong, most likely a weird USB descriptor. So the best option would be just to return an error at the parameter setup time before doing any further operations.
This patch introduces such a sanity check, and returns -EINVAL when the packet size is greater than maxpacksize. The comparison with ep->packsize[1] alone should suffice since it's always equal or greater than ep->packsize[0].
Which versions are affected by CVE-2025-40269?
How do I fix CVE-2025-40269?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2025-40269 being exploited?
There is no known exploitation of CVE-2025-40269 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-40269, DEBIAN-CVE-2025-40269, GHSA-7g56-9fh3-wcxw, ROOT-OS-DEBIAN-12-CVE-2025-40269, ROOT-OS-DEBIAN-13-CVE-2025-40269, ROOT-OS-UBUNTU-2204-CVE-2025-40269 and 2 more.