What is CVE-2021-41194?

CVE-2021-41194 is a critical-severity security vulnerability in jupyterhub-firstuseauthenticator (pip), affecting versions < 1.0.0. It is fixed in 1.0.0.

How severe is CVE-2021-41194?

CVE-2021-41194 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of jupyterhub-firstuseauthenticator are affected by CVE-2021-41194?

jupyterhub-firstuseauthenticator (pip) versions < 1.0.0 is affected.

Is there a fix for CVE-2021-41194?

Yes. CVE-2021-41194 is fixed in 1.0.0. Upgrade to this version or later.

Is CVE-2021-41194 exploitable, and should I be worried?

Whether CVE-2021-41194 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2021-41194 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2021-41194?

Upgrade jupyterhub-firstuseauthenticator to 1.0.0 or later.

CVE-2021-41194 in jupyterhub-firstuseauthenticator

Q: How severe is CVE-2021-41194?

CVE-2021-41194 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of jupyterhub-firstuseauthenticator are affected by CVE-2021-41194?

jupyterhub-firstuseauthenticator (pip) versions < 1.0.0 is affected.

Q: Is there a fix for CVE-2021-41194?

Yes. CVE-2021-41194 is fixed in 1.0.0. Upgrade to this version or later.

Q: Is CVE-2021-41194 exploitable, and should I be worried?

Whether CVE-2021-41194 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2021-41194 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2021-41194?

Upgrade jupyterhub-firstuseauthenticator to 1.0.0 or later.

Summary

Improper Access Control in jupyterhub-firstuseauthenticator

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.

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.

CVE-2021-41194 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.0.0); upgrading removes the vulnerable code path.

Affected versions

jupyterhub-firstuseauthenticator (< 1.0.0)

Security releases

jupyterhub-firstuseauthenticator → 1.0.0 (pip)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Upgrade to jupyterhub-firstuseauthenticator to 1.0, or apply patch https://github.com/jupyterhub/firstuseauthenticator/pull/38.patch

Frequently Asked Questions

What is CVE-2021-41194? CVE-2021-41194 is a critical-severity security vulnerability in jupyterhub-firstuseauthenticator (pip), affecting versions < 1.0.0. It is fixed in 1.0.0.
How severe is CVE-2021-41194? CVE-2021-41194 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of jupyterhub-firstuseauthenticator are affected by CVE-2021-41194? jupyterhub-firstuseauthenticator (pip) versions < 1.0.0 is affected.
Is there a fix for CVE-2021-41194? Yes. CVE-2021-41194 is fixed in 1.0.0. Upgrade to this version or later.
Is CVE-2021-41194 exploitable, and should I be worried? Whether CVE-2021-41194 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2021-41194 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2021-41194? Upgrade jupyterhub-firstuseauthenticator to 1.0.0 or later.