{"id":"CVE-2026-54338","summary":"JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","details":"JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. Prior to 5.5.0, invalid input to form-based login authenticators can place an unbounded attacker-controlled username in failed-login logs, allowing an unauthenticated attacker to consume logging and storage resources. This issue is fixed in version 5.5.0.","aliases":["GHSA-p43p-whwx-q52h"],"modified":"2026-08-12T03:51:29.896100389Z","published":"2026-08-07T20:52:55.068Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54338.json","unresolved_ranges":[{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"\u003c 5.5.0JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. Prior to 5.5.0, invalid input to form-based login authenticators can place an unbounded attacker-controlled username in failed-login logs, allowing an unauthenticated attacker to consume logging and storage resources. This issue is fixed in version 5.5.0."},{"last_affected":"\u003c 5.5.0JupyterHub is software that allows users to create a multi-user server for Jupyter notebooks. Prior to 5.5.0, invalid input to form-based login authenticators can place an unbounded attacker-controlled username in failed-login logs, allowing an unauthenticated attacker to consume logging and storage resources. This issue is fixed in version 5.5.0."}]}]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54338.json"},{"type":"ADVISORY","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":"FIX","url":"https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/jupyterhub/jupyterhub","events":[{"introduced":"0"},{"fixed":"d6dc595f84b7509969686da31d87d6d69e7fce0a"}],"database_specific":{"source":"REFERENCES"}}],"versions":["5.4.6","5.4.5","5.4.4","5.4.3","5.4.2","5.4.1","5.4.0","5.3.0","5.3.0rc0","5.2.1","5.2.0","5.1.0","5.0.0","5.0.0b2","5.0.0b1","4.0.1","4.0.0","4.0.0b2","4.0.0b1","3.1.0","3.0.0","3.0.0b1","2.2.2","2.2.1","2.2.0","2.1.1","2.1.0","2.0.2","2.0.1","2.0.0","2.0.0rc5","2.0.0rc4","2.0.0rc3","2.0.0rc2","2.0.0rc1","2.0.0b3","2.0.0b2","2.0.0b1","1.4.0","1.3.0","1.2.1","1.0.0","1.2.0","1.2.0b1","1.1.0","1.1.0b1","1.0.0b2","1.0.0b1","0.9.2","0.9.1","0.9.0","0.9.0rc1","0.9.0b3","0.9.0b2","0.9.0b1","0.8.1","0.8.0","0.8.0rc2","0.8.0rc1","0.8.0b5","0.8.0b4","0.8.0b3","0.8.0b2","0.8.0b1","0.7.2","0.7.1","0.7.0","0.6.1","0.6.0","0.5.0","0.4.1","0.4.0","0.3.0","0.2.0","0.1.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54338.json"}}],"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"}]}