Docling-Graph: SSRF via Missing Internal IP Validation in URLInputHandler

Docling-Graph turns documents into validated Pydantic objects, then builds a directed knowledge graph with explicit semantic relationships. Prior to 1.5.1, the URLInputHandler class in docling_graph/core/input/handlers.py makes HTTP requests to user-supplied URLs without validating whether the target resolves to a private, loopback, or link-local IP address. The URLValidator only checks for a valid scheme and non-empty netloc, performing no IP-level validation. Additionally, requests.head() was called with allow_redirects=True, allowing an attacker to redirect requests to internal endpoints via an intermediary URL. An attacker who can control the --source CLI argument or PipelineConfig.source API parameter can trigger Server-Side Request Forgery (SSRF). This vulnerability is fixed in 1.5.1.