CVE-2026-53921 odhcpd: Stack buffer overflow in DHCPv6 IA reply serialization (2 independent sites)

odhcpd is the DHCPv6, DHCPv4, and router-advertisement server used by OpenWrt. Prior to version 25.12, odhcpd's DHCPv6 IA response handler writes past the end of a fixed 512-byte stack buffer pdbuf when a single DHCPv6 REQUEST carries enough IA options to nearly exhaust the reply space. Two...