CVE-2026-23436 net: shaper: protect from late creation of hierarchy
A race condition in the Linux kernel network shaper allows memory leaks when a network device is unregistered during hierarchy creation, potentially leading to 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-2026-23436?
CVE-2026-23436 is a medium-severity vulnerability in Linux kernel, published on 3 Apr 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: shaper: protect from late creation of hierarchy
We look up a netdev during prep of Netlink ops (pre- callbacks) and take a ref to it. Then later in the body of the callback we take its lock or RCU which are the actual protections.
The netdev may get unregistered in between the time we take the ref and the time we lock it. We may allocate the hierarchy after flush has already run, which would lead to a leak.
Take the instance lock in pre- already, this saves us from the race and removes the need for dedicated lock/unlock callbacks completely. After all, if there's any chance of write happening concurrently with the flush - we're back to leaking the hierarchy.
We may take the lock for devices which don't support shapers but we're only dealing with SET operations here, not taking the lock would be optimizing for an error case.
Which versions are affected by CVE-2026-23436?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-23436?
Apply the vendor's patch.
Is CVE-2026-23436 being exploited?
There is no known exploitation of CVE-2026-23436 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-23436, DEBIAN-CVE-2026-23436, GHSA-943r-726h-fc9x, UBUNTU-CVE-2026-23436.