CVE-2026-72340 net: microchip: vcap: fix races on the shared Super VCAP block
A race condition in the Linux kernel's Microchip VCAP driver allows concurrent access to corrupt hardware entries, potentially causing data corruption or denial of service.
- 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-2026-72340?
CVE-2026-72340 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:
net: microchip: vcap: fix races on the shared Super VCAP block
The VCAP instances on a chip are not independent, yet they are locked independently. On sparx5 and lan969x the IS0 and IS2 instances are backed by the same Super VCAP hardware block and share its cache and command registers: every access drives the shared VCAP_SUPER_CTRL register and moves data through the shared cache registers.
Accessing one instance therefore races with accessing another. The per-instance admin->lock cannot prevent this, as each instance takes a different lock.
The locking issue is mostly disguised by the fact that the core usage of the vcap api runs under rtnl. However, the full rule dump in debugfs decodes rules straight from hardware (a READ command followed by a cache read) and runs outside rtnl, so it races a concurrent tc-flower rule write to another Super VCAP instance.
Besides corrupting the dump, the read repopulates the shared cache between the writers cache fill and its write command, so the writer commits the wrong data and corrupts the hardware entry.
Introduce vcap_lock() and vcap_unlock() helpers and route every rule lock site in the VCAP API and its debugfs code through them. Replace the per-instance admin->lock with a single mutex in struct vcap_control that serializes access to all instances. The helpers reach it through a new admin->vctrl back-pointer, and the clients initialise and destroy the control lock instead of a per-instance one.
No path holds more than one instance lock, so collapsing them onto a single mutex cannot self-deadlock.
Which versions are affected by CVE-2026-72340?
How do I fix CVE-2026-72340?
Apply the vendor's patch.
Is CVE-2026-72340 being exploited?
There is no known exploitation of CVE-2026-72340 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72340, DEBIAN-CVE-2026-72340, GHSA-57m3-p558-ghpc, UBUNTU-CVE-2026-72340.