Impact
When JupyterHub is used with FirstUseAuthenticator, the vulnerability allows unauthorized access to any user’s account if create_users=True and the username is known or guessed.
Patches
Upgrade to jupyterhub-firstuseauthenticator to 1.0, or apply patch https://github.com/jupyterhub/firstuseauthenticator/pull/38.patch
Workarounds
If you cannot upgrade, there is no complete workaround, but it can be mitigated.
If you cannot upgrade yet, you can disable user creation with c.FirstUseAuthenticator.create_users = False, which will only allow login with fully normalized usernames for already existing users prior to jupyterhub-firstuserauthenticator 1.0. If any users have never logged in with their normalized username (i.e. lowercase), they will still be vulnerable until you can patch or upgrade.
References
- https://github.com/jupyterhub/firstuseauthenticator/security/advisories/GHSA-5xvc-vgmp-jgc3
- https://nvd.nist.gov/vuln/detail/CVE-2021-41194
- https://github.com/jupyterhub/firstuseauthenticator/pull/38
- https://github.com/jupyterhub/firstuseauthenticator/pull/38.patch
- https://github.com/jupyterhub/firstuseauthenticator/pull/38/commits/32b21898fb2b53b1a2e36270de6854ad70e9e9bf
- https://github.com/jupyterhub/firstuseauthenticator/pull/38/commits/9e200d974e0cb85d828a6afedb8ab90a37878f28
- https://github.com/advisories/GHSA-5xvc-vgmp-jgc3