CVE-2026-74743

Summary

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.

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxb863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 < 8cd90e850e434577bf6774778657d26d6995e53faffected
LinuxLinuxb863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 < 28afc87bd8da0b3348bbbd834c8a89e83712cf5eaffected
LinuxLinuxb863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 < 8f6a05dbac05725e0786701eb04778c5bdbe4eaaaffected
LinuxLinuxb863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 < 96fa90b74385b7f2b0d97251dd43d5ee6ca44668affected
LinuxLinuxb863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 < bc9a00fb78e32bccc39d763bfd13a450705bac5daffected
LinuxLinuxb863ceb7ddcea8c55fcf1d7b2ac591d50aa7ed53 < cef51860becd9700217c81732ca1eb1ea6ed6fe1affected
LinuxLinux2.6.23affected
LinuxLinux0 < 2.6.23unaffected
LinuxLinux6.1.184 <= 6.1.*unaffected
LinuxLinux6.6.153 <= 6.6.*unaffected
LinuxLinux6.12.105 <= 6.12.*unaffected
LinuxLinux6.18.46 <= 6.18.*unaffected
LinuxLinux7.1.10 <= 7.1.*unaffected
LinuxLinux7.2 <= *unaffected

Weaknesses

References