CVE-2026-43026 netfilter: ctnetlink: zero expect NAT fields when CTA_EXPECT_NAT absent
An attacker can read stale kernel memory via netlink dumps when NAT fields are uninitialized, potentially exposing sensitive data.
- 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-2026-43026?
CVE-2026-43026 is a medium-severity vulnerability in Linux kernel, published on 1 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: zero expect NAT fields when CTA_EXPECT_NAT absent
ctnetlink_alloc_expect() allocates expectations from a non-zeroing slab cache via nf_ct_expect_alloc(). When CTA_EXPECT_NAT is not present in the netlink message, saved_addr and saved_proto are never initialized. Stale data from a previous slab occupant can then be dumped to userspace by ctnetlink_exp_dump_expect(), which checks these fields to decide whether to emit CTA_EXPECT_NAT.
The safe sibling nf_ct_expect_init(), used by the packet path, explicitly zeroes these fields.
Zero saved_addr, saved_proto and dir in the else branch, guarded by IS_ENABLED(CONFIG_NF_NAT) since these fields only exist when NAT is enabled.
Confirmed by priming the expect slab with NAT-bearing expectations, freeing them, creating a new expectation without CTA_EXPECT_NAT, and observing that the ctnetlink dump emits a spurious CTA_EXPECT_NAT containing stale data from the prior allocation.
Which versions are affected by CVE-2026-43026?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-43026?
Apply the vendor's patch.
Is CVE-2026-43026 being exploited?
There is no known exploitation of CVE-2026-43026 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-43026, DEBIAN-CVE-2026-43026, GHSA-x32p-2gcj-5qgh, ROOT-OS-DEBIAN-11-CVE-2026-43026, ROOT-OS-UBUNTU-2204-CVE-2026-43026, ROOT-OS-UBUNTU-2404-CVE-2026-43026 and 1 more.