GHSA-xf7x-x43h-rpqh

## Circular JSON Schema `$ref` causes unbounded CPU DoS in `json_repair` ### Summary `SchemaRepairer.resolve_schema()` in `json_repair` follows JSON Schema `$ref` pointers in an unbounded `while` loop without any cycle detection. An attacker who can supply a schema containing a self-referencing `$ref` (e.g., via the demo Flask API or any application that passes untrusted input to `loads(..., schema=...)`), can cause a worker process to spin indefinitely on CPU, resulting in a complete denial of service. No authentication is required against the public demo API. The vulnerability is confirmed reproducible at CVSS 7.5 (High). ### Details `SchemaRepairer.resolve_schema()` at `src/json_repair/schema_repair.py:184–190` resolves `$ref` chains using a plain `while` loop: ```python # src/json_repair/schema_repair.py:184-190 schema_dict = cast("dict[str, Any]", schema) while "$ref" in schema_dict: ref = schema_dict["$ref"] resolved = self._resolve_ref(ref) if isinstance(resolved, bool): return resolved schema_dict = resolved ``` `_resolve_ref()` at `src/json_repair/schema_repair.py:654–665` always resolves references relative to `self.root_schema`, which is initialised from the caller-supplied schema (`src/json_repair/schema_repair.py:130`). When the schema contains a circular reference such as: ```json {"$ref": "#/definitions/a", "definitions": {"a": {"$ref": "#/definitions/a"}}} ``` `_resolve_ref()` returns the same `dict` object on every iteration, so `"$ref" in schema_dict` is always `True` and the loop never terminates. The vulnerable sink is reachable without authentication through the demo Flask API: ```python # docs/app.py:14, 21-36 data = request.get_json() schema = data.get("schema") if schema is not None and not isinstance(schema, (dict, bool)): raise ValueError("schema must be a JSON object or boolean.") ... if schema is not None: loads_kwargs["schema"] = schema parsed_json = loads(malformed_json, **loads_kwargs) ``` The