CVE-2026-72340

What the bug is

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.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/net/ethernet/microchip/lan966x/lan966x_vcap_impl.c
drivers/net/ethernet/microchip/sparx5/sparx5_vcap_impl.c
drivers/net/ethernet/microchip/vcap/vcap_api.c
drivers/net/ethernet/microchip/vcap/vcap_api.h
drivers/net/ethernet/microchip/vcap/vcap_api_debugfs.c
drivers/net/ethernet/microchip/vcap/vcap_api_debugfs_kunit.c
drivers/net/ethernet/microchip/vcap/vcap_api_kunit.c
drivers/net/ethernet/microchip/vcap/vcap_api_private.h

What this is

MICROCHIP LAN966X ETHERNET DRIVERMAINTAINERS section matched on drivers/net/ethernet/microchip/lan966x/* · netdev@vger.kernel.org · Maintained

Check it on the machine

grep -wE 'CONFIG_ETHERNET|CONFIG_LAN966X_SWITCH|CONFIG_NET_VENDOR_MICROCHIP' /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian does not build this code in 3 releases. The build rule could not be established for 1 release, so nothing is claimed about those.

• bookworm?
• trixie, forky, sidn

?

not established - no Makefile entry for the affected file

n

not enabled on any flavour - this release does not build the code

Where a release above reads "not established", no build rule for the affected file was found in that release's kernel tree. That is a gap in this lookup, not a finding that the code is absent.

Build switches

CONFIG_ETHERNET, CONFIG_LAN966X_SWITCH, CONFIG_NET_VENDOR_MICROCHIP

Reads as

all on means the file is compiled; any one off means it is not.

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-08-15 (2 months ago)source

CVSS

7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it

Attack vector

local (AV:L)source

EPSS

0.18%, higher than 6.6% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

unimportantsource

Subsystem

drivers/net

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
6.2	6.6.145	786456d0a244
6.2	6.12.97	49806bef9572
6.2	6.18.40	1e71a40d1015
6.2	7.1.5	952928564cc5
6.2	7.2	d7a8d500d7e4