CVE-2026-74743

macvlan: inherit needed_headroom and needed_tailroom from lowerdev

State: Published
Severity: 9.8 Critical
Published: Aug 26, 2026
Updated: Oct 16, 2026
Reserved: Aug 15, 2026

Description

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

macvlan: inherit needed_headroom and needed_tailroom from lowerdev

macvlan devices inherit hard_header_len from lowerdev during macvlan_init(), but leave needed_headroom and needed_tailroom set to 0.

When the underlying lowerdev 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() / macvlan_hard_header() prepends header data or when lower devices append tailroom.

Fix this by: 1. Inheriting needed_headroom and needed_tailroom from lowerdev in macvlan_init(). 2. Propagating needed_headroom and needed_tailroom updates to attached macvlans in macvlan_device_event() when receiving NETDEV_FEAT_CHANGE events.

Scores

CVSS	Score	Vector	Source
3.1	9.8 Critical	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before c2ef3f134b069c54b9cc95cce1a16c38c4939336Affected b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 7b0eb3e0f363ca79a3af9efd2e87c6258f11da2bAffected b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 8cd90e850e434577bf6774778657d26d6995e53fAffected b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 28afc87bd8da0b3348bbbd834c8a89e83712cf5eAffected b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 8f6a05dbac05725e0786701eb04778c5bdbe4eaaAffected b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 96fa90b74385b7f2b0d97251dd43d5ee6ca44668Affected b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before bc9a00fb78e32bccc39d763bfd13a450705bac5dAffected b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before cef51860becd9700217c81732ca1eb1ea6ed6fe1Affected
LinuxLinux	2.6.23Affected before 2.6.23Not affected 5.10.271 through 5.10.Not affected 5.15.222 through 5.15.Not affected 6.1.184 through 6.1.Not affected 6.6.153 through 6.6.Not affected 6.12.105 through 6.12.Not affected 6.18.46 through 6.18.Not affected 7.1.10 through 7.1.*Not affected 7.2 and laterNot affected

Product

Versions

LinuxLinux

b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before c2ef3f134b069c54b9cc95cce1a16c38c4939336Affected
b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 7b0eb3e0f363ca79a3af9efd2e87c6258f11da2bAffected
b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 8cd90e850e434577bf6774778657d26d6995e53fAffected
b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 28afc87bd8da0b3348bbbd834c8a89e83712cf5eAffected
b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 8f6a05dbac05725e0786701eb04778c5bdbe4eaaAffected
b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before 96fa90b74385b7f2b0d97251dd43d5ee6ca44668Affected
b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before bc9a00fb78e32bccc39d763bfd13a450705bac5dAffected
b863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 to before cef51860becd9700217c81732ca1eb1ea6ed6fe1Affected

LinuxLinux

2.6.23Affected
before 2.6.23Not affected
5.10.271 through 5.10.*Not affected
5.15.222 through 5.15.*Not affected
6.1.184 through 6.1.*Not affected
6.6.153 through 6.6.*Not affected
6.12.105 through 6.12.*Not affected
6.18.46 through 6.18.*Not affected
7.1.10 through 7.1.*Not affected
7.2 and laterNot affected

References

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