CVE-2026-45331: Open WebUI has a full SSRF Vulnerability in the RAG Web Search Feature

validate_url() in backend/open_webui/retrieval/web/utils.py calls validators.ipv6(ip, private=True), but the validators library does NOT implement the private keyword for IPv6 — the call raises a ValidationError (which is falsy in a boolean context), so every IPv6 address passes the filter. In addition, IPv4-mapped IPv6 (::ffff:10.0.0.1) bypasses the IPv4 check entirely, and several reserved IPv4 ranges (0.0.0.0/8, 100.64.0.0/10, 192.0.0.0/24, etc.) are not blocked.

The vulnerability has existed since the validate_url() function was introduced and was NOT actually fixed by GHSA-c6xv-rcvw-v685 / CVE-2025-65958 despite that patch’s intent. It affects every endpoint that calls validate_url(), including /api/v1/retrieval/process/web, /api/v1/images/edit, and others.