CVE-2026-63994

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

tunnels: load network headers after skb_cow() in iptunnel_pmtud_build_icmpv6

Sashiko found that iptunnel_pmtud_build_icmp() and iptunnel_pmtud_build_icmpv6() were caching ip_hdr() and ipv6_hdr() before an skb_cow() call which can reallocate skb->head.

Fix this possible UAF by initializing the local variables after the skb_cow() call.

Remove skb_reset_network_header() calls which were not needed.