{"id":"CVE-2021-41194","aliases":["GHSA-5xvc-vgmp-jgc3","PYSEC-2021-384"],"title":"Improper Access Control in jupyterhub-firstuseauthenticator","summary":"Improper Access Control in jupyterhub-firstuseauthenticator","severity":"critical","cvss":9.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N","vendor":"jupyterhub-firstuseauthenticator","product":"jupyterhub-firstuseauthenticator","ecosystem":"pip","affected":["jupyterhub-firstuseauthenticator < 1.0.0"],"patched":["jupyterhub-firstuseauthenticator 1.0.0"],"published":"2021-10-28","updated":"2026-07-08","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-5xvc-vgmp-jgc3","references":[{"url":"https://github.com/jupyterhub/firstuseauthenticator/security/advisories/GHSA-5xvc-vgmp-jgc3"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-41194"},{"url":"https://github.com/jupyterhub/firstuseauthenticator/pull/38"},{"url":"https://github.com/jupyterhub/firstuseauthenticator/pull/38.patch"},{"url":"https://github.com/jupyterhub/firstuseauthenticator/pull/38/commits/32b21898fb2b53b1a2e36270de6854ad70e9e9bf"},{"url":"https://github.com/jupyterhub/firstuseauthenticator/pull/38/commits/9e200d974e0cb85d828a6afedb8ab90a37878f28"},{"url":"https://github.com/jupyterhub/firstuseauthenticator/commit/953418e2450dbc2d854e332350849533b0ebc7ba"},{"url":"https://github.com/jupyterhub/firstuseauthenticator"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/jupyterhub-firstuseauthenticator/PYSEC-2021-384.yaml"}],"tags":["osv","pip"],"epss":0.01367,"epssPercentile":0.70672,"ingestedAt":"2026-07-08T18:25:46.252Z","slug":"CVE-2021-41194","body":"## Overview\n\n### Impact\n\nWhen 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.\n\n### Patches\n\nUpgrade to jupyterhub-firstuseauthenticator to 1.0, or apply patch https://github.com/jupyterhub/firstuseauthenticator/pull/38.patch\n\n### Workarounds\n\nIf you cannot upgrade, there is no complete workaround, but it can be mitigated.\n\nIf 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.\n\n## Affected packages\n\n- `jupyterhub-firstuseauthenticator < 1.0.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `jupyterhub-firstuseauthenticator 1.0.0`","depth":"midnight","depthScore":50,"depthScoreParts":{"impact":50.1,"likelihood":0.3,"exploitation":0,"ransomware":0},"changes":[]}