CVE-2026-89562

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

ip6 gre: fix hardware header length for NBMA tunnels

ip6gre tnl link config route() accumulates the lower device's hardware header length into dev->hard header len whenever header ops is set. This is incorrect for both users of header ops.

ip6gretap and ip6erspan have a fixed Ethernet hardware header length. For an NBMA ip6gre tunnel, ip6gre header() creates only the GRE header, the optional FOU or GUE header, and the outer IPv6 header. The lower device header is headroom needed later, not part of the tunnel device's hardware header.

Keep the lower device header in needed headroom. Set hard header len to the tunnel header length only for ARPHRD IP6GRE devices with header ops, and leave the fixed Ethernet header length unchanged for tap and erspan devices.