CVE-2026-31424

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

netfilter: x_tables: restrict xt_check_match/xt_check_target extensions for NFPROTO_ARP

Weiming Shi says:

xt_match and xt_target structs registered with NFPROTO_UNSPEC can be

loaded by any protocol family through nft_compat. When such a

match/target sets .hooks to restrict which hooks it may run on, the

bitmask uses NF_INET_* constants. This is only correct for families

whose hook layout matches NF_INET_*: IPv4, IPv6, INET, and bridge

all share the same five hooks (PRE_ROUTING ... POST_ROUTING).

ARP only has three hooks (IN=0, OUT=1, FORWARD=2) with different

semantics. Because NF_ARP_OUT == 1 == NF_INET_LOCAL_IN, the .hooks

validation silently passes for the wrong reasons, allowing matches to

run on ARP chains where the hook assumptions (e.g. state->in being

set on input hooks) do not hold. This leads to NULL pointer

dereferences; xt_devgroup is one concrete example:

Oops: general protection fault, probably for

/// 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