CVE-2020-15110: Possible pod name collisions in jupyterhub-kubespawner

What kind of vulnerability is it? Who is impacted?

JupyterHub deployments using:

• KubeSpawner <= 0.11.1 (e.g. zero-to-jupyterhub 0.9.0) and
• enabled named_servers (not default), and
• an Authenticator that allows:
• usernames with hyphens or other characters that require escape (e.g. user-hyphen or user@email), and
• usernames which may match other usernames up to but not including the escaped character (e.g. user in the above cases)

In this circumstance, certain usernames will be able to craft particular server names which will grant them access to the default server of other users who have matching usernames.