GHSA-6r62-w2q3-48hf

Summary

BentoML's bentofile.yaml configuration allows path traversal attacks through multiple file path fields (description, docker.setup_script, docker.dockerfile_template, conda.environment_yml). An attacker can craft a malicious bentofile that, when built by a victim, exfiltrates arbitrary files from the filesystem into the bento archive. This enables supply chain attacks where sensitive files (SSH keys, credentials, environment variables) are silently embedded in bentos and exposed when pushed to registries or deployed.

Details

The vulnerability exists in how BentoML resolves user-provided file paths without validating that they remain within the build context directory.

Vulnerable function in src/bentoml/_internal/utils/filesystem.py:114-131:

def resolve_user_filepath(filepath: str, ctx: t.Optional[str]) -> str:
    _path = os.path.expanduser(os.path.expandvars(filepath))
    if not os.path.isabs(_path) and ctx:
        _path = os.path.expanduser(os.path.join(ctx, filepath))
    if os.path.exists(_path):
        return os.path.realpath(_path)  # No path containment check
    raise FileNotFoundError(f"file {filepath} not found")

Vulnerable code in src/bentoml/_internal/bento/bento.py:348-355:

if build_config.description.startswith("file:"):
    file_name = build_config.description[5:].strip()
    if not ctx_path.joinpath(file_name).exists():
        raise InvalidArgument(f"File {file_name} does not exist.")
    shutil.copy(ctx_path.joinpath(file_name), bento_readme)  # Path traversal

All four vulnerable fields:

• description: "file:../../../etc/passwd" → copied to README.md
• docker.setup_script: "../../../etc/passwd" → copied to env/docker/setup_script
• docker.dockerfile_template: "../../../secret" → copied to env/docker/Dockerfile.template
• conda.environment_yml: "../../../etc/hosts" → copied to env/conda/environment.yml

**Multiple path formats are supported, making...