CVE-2026-80824

In the Linux kernel, the following vulnerability has been resolved:

usb: usbfs: fix use-after-free of usb device in usbdev release()

usbdev release() drops its reference to the struct usb device before draining the list of completed async URBs, but that drain path reads back through the same object: free async() calls dec usb memory use count() for any URB whose buffer came from the usbfs mmap() region, and its first statement is bus to hcd(ps->dev->bus).

After a disconnect the usbfs reference can be the last one, in which case usb put dev() frees the device and the subsequent loop reads offset 80 of freed memory and uses the result as a struct usb hcd *, which hcd buffer free pages() then dereferences.

This is reachable by an unprivileged process that has read/write access to a /dev/bus/usb node: mmap() the fd, submit one URB with a buffer inside the mapping, wait for the device to be unplugged, then munmap() and close(). It reproduces on every attempt rather than being a race, because a live MAP SHARED vma holds a reference on the struct file, so usbdev release() cannot run until the last vma is gone and the freeing branch of dec usb memory use count() is always taken.

BUG: KASAN: slab-use-after-free in dec usb memory use count+0x3ae/0x410 Read of size 8 at addr ffff8880122ee050 by task poc/769 CPU: 1 UID: 1000 PID: 769 Comm: poc Tainted: G B 6.12.94 #3

Call Trace: dec usb memory use count+0x3ae/0x410 free async+0x2aa/0x4f0 usbdev release+0x375/0x460 fput+0x3ea/0xb50 x64 sys close+0x86/0x100

Allocated by task 11: usb alloc dev+0x55/0xd90 hub event+0x2524/0x43d0

Freed by task 769: kfree+0x121/0x360 device release+0xd2/0x280 usb put dev+0x23/0x30 usbdev release+0x2d8/0x460

Release the device reference after the drain loop instead. Nothing between the two points requires it to have been dropped.