CVE-2026-98301 net: bridge: mst: move switchdev call outside rcu
A sleeping function called from invalid context in the Linux kernel bridge MST code can cause a system crash or denial of service.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-98301?
CVE-2026-98301 is a denial of service vulnerability in Linux, published on 6 Oct 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: bridge: mst: move switchdev call outside rcu
This is a follow-up of one of sashiko's pre-existing bug reports. br_mst_set_state() calls switchdev_port_attr_set() for nonzero MSTIs while holding rcu_read_lock() which invokes the blocking switchdev notifier chain and may sleep. Nonzero MSTI changes come from netlink with rtnl held. Move the switchdev call before entering the rcu section and assert that rtnl is held.
The call cannot be deferred because netlink needs its error and extack. Also DSA reads the old bridge MST state during the callback and checks it. A deferred callback will be late and will see the updated state.
Which versions are affected by CVE-2026-98301?
How do I fix CVE-2026-98301?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-98301 being exploited?
There is no known exploitation of CVE-2026-98301 in the wild and no public exploit code.
Sources
Also known as AZL-106266, BELL-CVE-2026-98301, DEBIAN-CVE-2026-98301, GHSA-rcgj-3ccr-mx7g, UBUNTU-CVE-2026-98301.