CVE-2026-43116 netfilter: ctnetlink: ensure safe access to master conntrack
A race condition in the Linux kernel netfilter ctnetlink module allows invalid memory access, potentially causing a system crash.
- 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-2026-43116?
CVE-2026-43116 is a high-severity vulnerability in Linux kernel, published on 6 May 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:
netfilter: ctnetlink: ensure safe access to master conntrack
Holding reference on the expectation is not sufficient, the master conntrack object can just go away, making exp->master invalid.
To access exp->master safely:
- Grab the nf_conntrack_expect_lock, this gets serialized with clean_from_lists() which also holds this lock when the master conntrack goes away.
- Hold reference on master conntrack via nf_conntrack_find_get(). Not so easy since the master tuple to look up for the master conntrack is not available in the existing problematic paths.
This patch goes for extending the nf_conntrack_expect_lock section to address this issue for simplicity, in the cases that are described below this is just slightly extending the lock section.
The add expectation command already holds a reference to the master conntrack from ctnetlink_create_expect().
However, the delete expectation command needs to grab the spinlock before looking up for the expectation. Expand the existing spinlock section to address this to cover the expectation lookup. Note that, the nf_ct_expect_iterate_net() calls already grabs the spinlock while iterating over the expectation table, which is correct.
The get expectation command needs to grab the spinlock to ensure master conntrack does not go away. This also expands the existing spinlock section to cover the expectation lookup too. I needed to move the netlink skb allocation out of the spinlock to keep it GFP_KERNEL.
For the expectation events, the IPEXP_DESTROY event is already delivered under the spinlock, just move the delivery of IPEXP_NEW under the spinlock too because the master conntrack event cache is reached through exp->master.
While at it, add lockdep notations to help identify what codepaths need to grab the spinlock.
Weakness: CWE-362
Which versions are affected by CVE-2026-43116?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43116?
Apply the vendor's patch.
Is CVE-2026-43116 being exploited?
There is no known exploitation of CVE-2026-43116 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-85851, BELL-CVE-2026-43116, DEBIAN-CVE-2026-43116, GHSA-88rv-c8gv-rfv7, ROOT-OS-DEBIAN-11-CVE-2026-43116, ROOT-OS-DEBIAN-12-CVE-2026-43116 and 4 more.