CVE-2026-64554 netfilter: bridge: fix stale prevhdr pointer in br_ip6_fragment()

In the Linux kernel, the following vulnerability has been resolved: netfilter: bridge: fix stale prevhdr pointer in brip6fragment brip6fragment gets prevhdr, a pointer into the skb head, from ip6find1stfragopt, then calls skbchecksumhelp. For a cloned skb skbchecksumhelp reallocates the head via...