MLflow vulnerable to arbitrary file read on unauthenticated servers via prompt model version source

Summary

On MLflow tracking servers running without authentication, which is the default for mlflow server, a remote attacker can read arbitrary files from the server’s filesystem by creating a model version tagged as a prompt whose source is a schemeless local path.

The fix for CVE-2026-2614 in 3.10.0 added a prompt-specific branch to the CreateModelVersion handler that rejects file:// URIs and absolute paths but runs path validation only when the source carries a URL scheme. A schemeless value such as ../../etc, a plain relative name, ., a percent-encoded path, or a Windows drive-letter path is therefore stored unchanged as the model version’s artifact location, and the model-versions/get-artifact endpoint later serves files from it with the privileges of the server process. The tag check also keyed on the presence of the mlflow.prompt.is_prompt tag rather than its value, so a false value still selected the weaker branch.

Servers using --app-name basic-auth are also affected: any authenticated user can create a registered model, so a low-privilege account can use this to read the authentication database, including the admin password hash.

Affected: MLflow 3.10.0 through 3.16.1. Fixed in 3.17.0 by mlflow/mlflow#25870, which accepts only MLflow’s own placeholder sources for prompt versions and requires the prompt tag to be true.

Details

When creating a model version with the mlflow.prompt.is_prompt tag set to true, the request is handled by the prompt branch in _create_model_version().

mlflow/server/handlers.py:2674-2690:

is_prompt = _is_prompt_request(request_message)
if is_prompt:
    source = request_message.source
    parsed = urllib.parse.urlparse(source)
    if parsed.scheme == "file" or (parsed.scheme == "" and source.startswith("/")):
        raise MlflowException(...)
    if parsed.scheme:
        _validate_non_local_source_contains_relative_paths(source)
else:
    if request_message.model_id:
        _validate_source_model(request_message.source, request_message.model_id)
    else:
        _validate_source_run(request_message.source, request_message.run_id)