Copyright © 2012 Red Hat, Inc. All rights reserved. Important 2026-08-26T00:00:00 kernel: macvlan: inherit needed_headroom and needed_tailroom from lowerdev 7.0 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H CWE-124

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.

A flaw was found in the Linux kernel's macvlan component. The macvlan component incorrectly initializes network packet buffer (skb) headroom and tailroom values, failing to inherit them from the underlying network device. This can occur when the underlying device requires additional space for headers or trailers, such as with macsec or IPsec. This oversight can lead to memory corruption, specifically KASAN slab-use-after-free crashes, potentially resulting in a denial of service.

Red Hat Enterprise Linux 10 Affected kernel Red Hat Enterprise Linux 6 Under investigation kernel Red Hat Enterprise Linux 7 Affected kernel Red Hat Enterprise Linux 7 Affected kernel-rt Red Hat Enterprise Linux 8 Affected kernel Red Hat Enterprise Linux 8 Affected kernel-rt Red Hat Enterprise Linux 9 Affected kernel Red Hat Enterprise Linux 9 Affected kernel-rt https://www.cve.org/CVERecord?id=CVE-2026-74743 https://nvd.nist.gov/vuln/detail/CVE-2026-74743 https://lore.kernel.org/linux-cve-announce/2026082658-CVE-2026-74743-ba1f@gregkh/T