CVE-2026-74667
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.
CSIRTS triage
- What
- A vulnerability in the packet socket transmit path where the MAC header is not properly reset, potentially leaking header information.
- Who is affected
- Systems running affected Linux kernel versions transmitting packets via packet sockets.
- Urgency
- Medium priority; not exploited but can leak network header metadata across packets.
- Action
- Apply Linux kernel patch resetting the MAC header on packet-socket transmit path.
AI-assisted analysis generated from the source advisory — verify against the original.
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Exploitation outlook
- Low exploitation risk0.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 8% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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