CVE-2026-64331 usbip: vudc: fix NULL deref in vep_dequeue()
A NULL pointer dereference in the Linux kernel's USBIP vudc driver allows local attackers to cause a system crash via FunctionFS AIO cancellations.
- 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-2026-64331?
CVE-2026-64331 is a medium-severity vulnerability in Linux kernel, published on 25 Jul 2026. 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:
usbip: vudc: fix NULL deref in vep_dequeue()
vep_alloc_request() wasn't initializing vrequest->udc, so cancellations on the FunctionFS AIO path were arriving in vep_dequeue without a valid UDC reference.
Since vrequest->udc is never actually properly used anywhere, we opt to remove it, and update vep_dequeue to obtain a reference to the udc with ep_to_vudc(), consistent with the other vep_ ops.
AFAICT this bug has existed for ~10 years. Seems that nobody has really stressed the FunctionFS AIO path on usbip's vudc.
I tested this fix in a QEMU aarch64 guest driving FunctionFS endpoints via AIO. Before the fix, running `usbip attach` from the host would cause the guest to oops with the following backtrace:
Call trace: vep_dequeue+0x1c/0xe4 (P) usb_ep_dequeue+0x14/0x20 ffs_aio_cancel+0x24/0x34 __arm64_sys_io_cancel+0xb0/0x124 do_el0_svc+0x68/0x100 el0_svc+0x18/0x5c el0t_64_sync_handler+0x98/0xdc el0t_64_sync+0x154/0x158
Weakness: CWE-476
Which versions are affected by CVE-2026-64331?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-64331?
Apply the vendor's patch.
Is CVE-2026-64331 being exploited?
There is no known exploitation of CVE-2026-64331 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-64331, DEBIAN-CVE-2026-64331, GHSA-x846-472j-jj99, ROOT-OS-UBUNTU-2204-CVE-2026-64331, UBUNTU-CVE-2026-64331.