CVE-2026-72254 netfilter: nft_fib: reject fib expression on the netdev egress hook
A NULL pointer dereference in the Linux kernel netfilter module allows local attackers to cause a system crash by using specific FIB expressions on the netdev egress hook.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-72254?
CVE-2026-72254 is a high-severity vulnerability in Linux, published on 15 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_fib: reject fib expression on the netdev egress hook
A fib expression in a netdev egress base chain dereferences nft_in(pkt), NULL on the transmit path, causing a NULL pointer dereference at eval. nft_fib_validate() masks the hook with NF_INET_* values, but netdev hook numbers are a separate enum that aliases them (NF_NETDEV_EGRESS == NF_INET_LOCAL_IN), so an egress chain passes validation and then faults.
Add nft_fib_netdev_validate() that limits each result/flag to the netdev hook where the device it reads exists: the input-device cases (OIF, OIFNAME, ADDRTYPE with F_IIF) to ingress, the output-device case (ADDRTYPE with F_OIF) to egress, ADDRTYPE with no device flag to both. Also restrict nft_fib_validate() to NFPROTO_IPV4/IPV6/INET so its NF_INET_* masks are not applied to another family's hooks.
Which versions are affected by CVE-2026-72254?
How do I fix CVE-2026-72254?
Apply the vendor's patch.
Is CVE-2026-72254 being exploited?
There is no known exploitation of CVE-2026-72254 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-72254, DEBIAN-CVE-2026-72254, GHSA-f5p7-25h5-xxwh, UBUNTU-CVE-2026-72254.