PYSEC-2026-2978 Pydantic AI: SSRF cloud-metadata blocklist bypass via IPv4-mapped IPv6 (Incomplete fix of CVE-2026-25580)

Summary When an application using Pydantic AI opts a URL into forcedownload='allow-local' which disables the default block on private/internal IPs, the cloud-metadata blocklist could be bypassed by encoding the metadata IP in an IPv6 transition form IPv4-mapped IPv6, 6to4, or NAT64. Dual-stack an...