CVE-2026-52942

/// Technical description

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

netfilter: nf_log: validate MAC header was set before dumping it

The fallback path of dump_mac_header() guards the MAC header access

only with "skb->mac_header != skb->network_header", without checking

skb_mac_header_was_set(). When the MAC header is unset, mac_header is

0xffff, so the test passes and skb_mac_header(skb) returns

skb->head + 0xffff, ~64 KiB past the buffer; the loop then reads

dev->hard_header_len bytes out of bounds into the kernel log.

This is reachable via the netdev logger: nf_log_unknown_packet() calls

dump_mac_header() unconditionally, and an skb sent through AF_PACKET

with PACKET_QDISC_BYPASS reaches the egress hook with mac_header still

unset (__dev_queue_xmit(), which would reset it, is bypassed).

Add the skb_mac_header_was_set() check the ARPHRD_ETHER path already

uses, and replace the open-coded MAC header length test with

skb_mac_header_len(). Only skbs with an unset MAC header are affec

/// 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