CVE-2026-72254

/// Technical 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.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References