Model Context Protocol Python SDK: Client fetched server-chosen $ref URLs while validating tool results against output schemas

影響: pip:mcp >= 2.0.0, < 2.2.0 → 2.2.0, pip:mcp >= 1.10.0, < 1.30.0 → 1.30.0

In affected versions, when a connected MCP server declared an outputSchema for a tool, the SDK's client validated each call_tool result with jsonschema's default resolver, which fetches any $ref it cannot resolve locally by opening the URL. A server could therefore put an http://, https:// or file:// reference in a tool's output schema and make the client: - request that URL, or read that local file, from the client's own network position on every call of the tool (the content was used only as…

GitHub Advisory Databaseで読む

2026/10/28 06:05、GitHub Advisory Databaseが「Model Context Protocol Python SDK: Client fetched server-chosen $ref URLs while validating tool results against output schemas」を公開しました (種別: 脆弱性アドバイザリ)。重大度は「警告」(medium) です。関連する技術: Python。CVE: CVE-2026-116686。