CVE-2026-63874 net: mctp: usb: fix race between urb completion and rx_retry cancellation
A race condition in the Linux kernel MCTP USB driver can lead to a denial of service by improperly handling URB completion and work cancellation.
- 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-2026-63874?
CVE-2026-63874 is a high-severity vulnerability in Linux, published on 19 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:
net: mctp: usb: fix race between urb completion and rx_retry cancellation
It's possible that sequencing between setting ->stopped and cancelling the rx_retry work (in ndo_stop) could leave us with an urb queued:
T1: ndo_stop T2: rx_retry_work ------------ ---------------- LD: ->stopped => false ST: ->stopped <= true usb_kill_urb() mctp_usb_rx_queue() usb_submit_urb() cancel_delayed_work_sync()
That urb completion can then re-schedule rx_retry_work.
Strenghen the sequencing between the stop (preventing another requeue) and the cancel by updating both atomically under a new rx lock. After setting ->rx_stopped, and cancelling pending work, we know that the requeue cannot occur, so all that's left is killing any pending urb.
Which versions are affected by CVE-2026-63874?
How do I fix CVE-2026-63874?
Apply the vendor's patch.
Is CVE-2026-63874 being exploited?
There is no known exploitation of CVE-2026-63874 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-63874, DEBIAN-CVE-2026-63874, GHSA-4gv8-vfvf-62f2, UBUNTU-CVE-2026-63874.