CVE-2026-72122 can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
A race condition in the Linux kernel CAN BCM module allows bypassing interface binding restrictions, potentially exposing traffic to unintended interfaces.
- 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-2026-72122?
CVE-2026-72122 is a high-severity vulnerability in Linux, published on 15 Aug 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:
can: bcm: fix lockless bound/ifindex race and silent RX_SETUP failure
bcm_sendmsg() reads bo->ifindex and checks bo->bound before taking lock_sock(), while bcm_notify(), bcm_connect() and bcm_release() all mutate both fields under that same lock. Because the lockless reads and the locked writes are unordered with respect to each other, a racing bcm_notify() (device unregister) or bcm_connect() (concurrent bind on another thread sharing the socket) can make bcm_sendmsg() observe an inconsistent combination, e.g. a stale bound=1 together with the now-cleared ifindex=0, silently turning a socket bound to a specific CAN interface into one that also matches "any" interface.
Keep the lockless bo->bound check purely as a fast-path reject, and move the ifindex read (and a bo->bound re-check) into the locked section, where every writer already serializes. This removes the possibility of observing the two fields torn against each other, rather than trying to fix it with more READ_ONCE()/WRITE_ONCE() pairs on two independently updated fields. Annotate the now-purely-lockless bo->bound accesses consistently across all its write sites.
Also fix bcm_rx_setup() silently returning success when the target device disappears concurrently instead of reporting -ENODEV, so a broken RX op is no longer left registered as if it had succeeded.
Which versions are affected by CVE-2026-72122?
How do I fix CVE-2026-72122?
Apply the vendor's patch.
Is CVE-2026-72122 being exploited?
There is no known exploitation of CVE-2026-72122 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72122, DEBIAN-CVE-2026-72122, GHSA-4cqx-6pr4-c34w, UBUNTU-CVE-2026-72122.