Improper Access Control in jupyterhub-firstuseauthenticator
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.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Python (PyPI) | jupyterhub-firstuseauthenticator | < 1.0.0 | 1.0.0 |
References
- https://github.com/jupyterhub/firstuseauthenticator/pull/38.patch
- https://github.com/jupyterhub/firstuseauthenticator/security/advisories/GHSA-5xvc-vgmp-jgc3
- https://github.com/jupyterhub/firstuseauthenticator/pull/38
- https://nvd.nist.gov/vuln/detail/CVE-2021-41194
- https://github.com/jupyterhub/firstuseauthenticator/pull/38/commits/32b21898fb2b53b1a2e36270de6854ad70e9e9bf
- https://github.com/jupyterhub/firstuseauthenticator/pull/38/commits/9e200d974e0cb85d828a6afedb8ab90a37878f28
- https://github.com/jupyterhub/firstuseauthenticator/commit/953418e2450dbc2d854e332350849533b0ebc7ba
- https://github.com/jupyterhub/firstuseauthenticator
- https://github.com/pypa/advisory-database/tree/main/vulns/jupyterhub-firstuseauthenticator/PYSEC-2021-384.yaml
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N- Weakness (CWE)
CWE-284- Platform
- Python (PyPI)
- Package
jupyterhub-firstuseauthenticator- Disclosed
- 28.10.2021
- Updated
- 11.10.2026 13:19
Sources and licenses
OSV / GitHub Advisory Database - PYSEC-2021-384 - PyPA Advisory Database; CC BY 4.0
OSV / GitHub Advisory Database - GHSA-5xvc-vgmp-jgc3 - CC BY 4.0
Vulnerability history: jupyterhub-firstuseauthenticator
All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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