CVE-2021-41194 Improper Access Control in jupyterhub-firstuseauthenticator

What is CVE-2021-41194?

CVE-2021-41194 is a critical authentication bypass vulnerability in jupyterhub firstuseauthenticator, published on 28 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

FirstUseAuthenticator is a JupyterHub authenticator that helps new users set their password on their first login to JupyterHub. When JupyterHub is used with FirstUseAuthenticator, a vulnerability in versions prior to 1.0.0 allows unauthorized access to any user's account if `create_users=True` and the username is known or guessed. One may upgrade to version 1.0.0 or apply a patch manually to mitigate the vulnerability. For those who cannot upgrade, there is no complete workaround, but a partial mitigation exists. One 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 1.0.0. If any users have never logged in with their normalized username (i.e. lowercase), they will still be vulnerable until a patch or upgrade occurs.

Weakness: CWE-284

Which versions are affected by CVE-2021-41194?

3 open source packages ship an affected version, including jupyterhub-firstuseauthenticator. It affects 1 product.

Products include Jupyterhub First Use Authenticator.

How do I fix CVE-2021-41194?

Upgrade jupyterhub-firstuseauthenticator to 1.0.0 or later.

Upgrade, and rotate credentials and sessions that may have been exposed. More about Authentication bypass.

Is CVE-2021-41194 being exploited?

There is no known exploitation of CVE-2021-41194 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-5xvc-vgmp-jgc3, PYSEC-2021-384.