CVE-2026-74667

Summary

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

net/packet: reset the MAC header on the packet-socket transmit path

packet_parse_headers() resets the MAC header only for a SOCK_RAW frame whose socket did not bind a protocol. A protocol-bound SOCK_RAW socket, any SOCK_DGRAM frame, and the legacy SOCK_PACKET path therefore leave skb->mac_header unset here.

For frames sent via __dev_queue_xmit() this is harmless: it resets the MAC header unconditionally. But the packet-socket PACKET_QDISC_BYPASS path uses dev_direct_xmit(), which does not, so the frame reaches ndo_start_xmit() with the MAC header unset. A driver that reads eth_hdr(skb) on transmit then dereferences skb->head + (u16)~0, an out-of-bounds access ~64 KiB past the head – the same class fixed for one consumer in commit f5089008f90c ("macsec: do not read an unset MAC header in macsec_encrypt()").

packet_parse_headers() runs only on the transmit path, where skb->data points at the start of the L2 header for every packet-socket type regardless of its length: SOCK_RAW and SOCK_PACKET carry a user-supplied header and SOCK_DGRAM has one built by dev_hard_header(). Reset the MAC header unconditionally, mirroring __dev_queue_xmit(), so the frame is anchored on the bypass path too.

Found by 0sec (https://0sec.ai) using automated source analysis; verified against source and matched to the macsec KASAN report in f5089008f90c. Compile-tested.

Affected Software

VendorProductVersion RangeStatus
LinuxLinux75c65772c3d18447d62d3aca5f91b06c16cc25e4 < 1e43a1d66615f411d427f9df1f46dd049d9e3681affected
LinuxLinux75c65772c3d18447d62d3aca5f91b06c16cc25e4 < 4057853a91fb796c4f47c7d1baf1aa085394148eaffected
LinuxLinux75c65772c3d18447d62d3aca5f91b06c16cc25e4 < 2610ed4e86a4590234a9d70518c469751c5af231affected
LinuxLinux75c65772c3d18447d62d3aca5f91b06c16cc25e4 < b47ba8fe6e1d2df8c92048de5afafd059447dc30affected
LinuxLinux75c65772c3d18447d62d3aca5f91b06c16cc25e4 < 284f3e7a3f1a743fdf89e304fd1f19d5ffcff46daffected
LinuxLinux75c65772c3d18447d62d3aca5f91b06c16cc25e4 < 971aa7d99242bbf09513e27b7a243f0b29ff23aeaffected
LinuxLinux75c65772c3d18447d62d3aca5f91b06c16cc25e4 < fdd4d7d52358a58e351dd9d82530c04eba8ccd7aaffected
LinuxLinux75c65772c3d18447d62d3aca5f91b06c16cc25e4 < c2707480cfbf19c7619acc9c089d17f20869821faffected
LinuxLinux5.1affected
LinuxLinux0 < 5.1unaffected
LinuxLinux5.10.265 <= 5.10.*unaffected
LinuxLinux5.15.216 <= 5.15.*unaffected
LinuxLinux6.1.183 <= 6.1.*unaffected
LinuxLinux6.6.152 <= 6.6.*unaffected
LinuxLinux6.12.104 <= 6.12.*unaffected
LinuxLinux6.18.45 <= 6.18.*unaffected
LinuxLinux7.1.9 <= 7.1.*unaffected
LinuxLinux7.2 <= *unaffected

Weaknesses

References