{"id":"PYSEC-2026-3853","summary":"JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","details":"### Impact\n\nInvalid input to login resulted in unbounded logging output. Only form-based Authenticators (the default PAM Authenticator, but not the more widely used OAuthenticator) are affected.\n\n### Patches\n\nUpgrade to 5.5.0.\n\n### Workarounds\n\nUse an Authenticator that doesn't use a login form, such as OAuthenticator.","aliases":["CVE-2026-54338","GHSA-p43p-whwx-q52h"],"modified":"2026-09-10T12:15:03.037930951Z","published":"2026-09-10T09:44:57.193967Z","references":[{"type":"WEB","url":"https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-p43p-whwx-q52h"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54338"},{"type":"WEB","url":"https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a"},{"type":"PACKAGE","url":"https://github.com/jupyterhub/jupyterhub"},{"type":"PACKAGE","url":"https://pypi.org/project/jupyterhub"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-p43p-whwx-q52h"}],"affected":[{"package":{"name":"jupyterhub","ecosystem":"PyPI","purl":"pkg:pypi/jupyterhub"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.5.0"}]}],"versions":["0.1.0","0.2.0","0.3.0","0.4.0","0.4.1","0.5.0","0.6.0","0.6.1","0.7.0","0.7.0b1","0.7.1","0.7.2","0.8.0","0.8.0b1","0.8.0b2","0.8.0b3","0.8.0b4","0.8.0b5","0.8.0rc1","0.8.0rc2","0.8.1","0.9.0","0.9.0b1","0.9.0b2","0.9.0b3","0.9.0rc1","0.9.1","0.9.2","0.9.3","0.9.4","0.9.5","0.9.6","1.0.0","1.0.0b1","1.0.0b2","1.1.0","1.1.0b1","1.2.0","1.2.0b1","1.2.1","1.2.2","1.3.0","1.4.0","1.4.1","1.4.2","1.5.0","1.5.1","2.0.0","2.0.0b1","2.0.0b2","2.0.0b3","2.0.0rc1","2.0.0rc2","2.0.0rc3","2.0.0rc4","2.0.0rc5","2.0.1","2.0.2","2.1.0","2.1.1","2.2.0","2.2.1","2.2.2","2.3.0","2.3.1","3.0.0","3.0.0b1","3.1.0","3.1.1","4.0.0","4.0.0b1","4.0.0b2","4.0.1","4.0.2","4.1.0","4.1.1","4.1.2","4.1.3","4.1.4","4.1.5","4.1.6","5.0.0","5.0.0b1","5.0.0b2","5.1.0","5.2.0","5.2.1","5.3.0","5.3.0rc0","5.4.0","5.4.1","5.4.2","5.4.3","5.4.4","5.4.5","5.4.6"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/jupyterhub/PYSEC-2026-3853.yaml"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}