CVE-2026-31738 vxlan: validate ND option lengths in vxlan_na_create

In the Linux kernel, the following vulnerability has been resolved: vxlan: validate ND option lengths in vxlannacreate vxlannacreate walks ND options according to option-provided lengths. A malformed option can make the parser advance beyond the computed option span or use a too-short source LLAD...