Advisories for Pypi/Jupyter-Server-Proxy package

There is a reflected cross-site scripting (XSS) issue in jupyter-server-proxy[1]. The /proxy endpoint accepts a host path segment in the format /proxy/<host>. When this endpoint is called with an invalid host value, jupyter-server-proxy replies with a response that includes the value of host, without sanitization [2]. A third-party actor can leverage this by sending a phishing link with an invalid host value containing custom JavaScript to a user. When the …

jupyter-server-proxy is used to expose ports local to a Jupyter server listening to web traffic to the Jupyter server's authenticated users by proxying web requests and websockets. Dependent packages (partial list) also use jupyter-server-proxy to expose other popular interactive applications (such as RStudio, Linux Desktop via VNC, Code Server, Panel, etc) along with the Jupyter server. This feature is commonly used in hosted environments (such as a JupyterHub) to expose …

What kind of vulnerability is it? Server-Side Request Forgery ( SSRF ) Who is impacted? Any user deploying Jupyter Server or Notebook with jupyter-proxy-server extension enabled. A lack of input validation allowed authenticated clients to proxy requests to other hosts, bypassing the allowed_hosts check. Because authentication is required, which already grants permissions to make the same requests via kernel or terminal execution, this is considered low to moderate severity.