CVE-2026-80104: DB-GPT builds the destination path for an uploaded skill from the multipart filename without constraining it to the uplo

DB-GPT builds the destination path for an uploaded skill from the multipart filename without constraining it to the upload directory. skill_upload in packages/dbgpt-app/src/dbgpt_app/openapi/api_v1/agentic_data_api.py takes file.filename as given and writes the request body to upload_dir / filename. A path composed with that operator discards the left operand when the right one is absolute and follows parent references otherwise, so a filename such as ../../../tmp/x or /tmp/x resolves outside the intended directory; nothing canonicalises the result, checks that it remains under the upload root, or prevents a .py suffix. The route's only dependency is get_user_from_headers in dbgpt_serve/utils/auth.py, which returns a request carrying the admin role whether or not a user_id header is supplied, so the endpoint is reachable without credentials. A remote attacker holding no account can therefore write attacker-controlled bytes to any path the server process can write, place a new Python module inside the application package or replace one the application already imports, and obtain code execution in the server process when that module is next imported.