{"id":"CVE-2026-54338","aliases":["GHSA-p43p-whwx-q52h"],"url":"https://o3.security/vulnerability/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.","published":"2026-08-07T20:52:55.068Z","modified":"2026-08-12T03:51:29.896100389Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"jupyterhub","fixedVersion":"5.5.0"}],"fix":{"url":"https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a","label":"jupyterhub/jupyterhub@d6dc595"},"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:29.896100389Z"}}