Description

Cross site scripting (XSS) in JupyterHub via Self-XSS leveraged by Cookie Tossing

Impact

Affected configurations:

Single-origin JupyterHub deployments

JupyterHub deployments with user-controlled applications running on subdomains or peer subdomains of either the Hub or a single-user server.

By tricking a user into visiting a malicious subdomain, the attacker can achieve an XSS directly affecting the former's session. More precisely, in the context of JupyterHub, this XSS could achieve the following:

Full access to JupyterHub API and user's single-user server, e.g.

Create and exfiltrate an API Token

Exfiltrate all files hosted on the user's single-user server: notebooks, images, etc.

Install malicious extensions. They can be used as a backdoor to silently regain access to victim's session anytime.

Patches

To prevent cookie-tossing:

Upgrade to JupyterHub 4.1 (both hub and user environment)

enable per-user domains via c.JupyterHub.subdomain_host = "https://mydomain.example.org"

set c.JupyterHub.cookie_host_prefix_enabled = True to enable domain-locked cookies

or, if available (applies to earlier JupyterHub versions):

deploy jupyterhub on its own domain, not shared with any other services

enable per-user domains via c.JupyterHub.subdomain_host = "https://mydomain.example.org"

Mitigation

Aliases

References