{"id":"CVE-2026-54338","aliases":["GHSA-p43p-whwx-q52h","PYSEC-2026-3853"],"title":"JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","summary":"JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","severity":"medium","cvss":5.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","vendor":"jupyterhub","product":"jupyterhub","ecosystem":"pip","affected":["jupyterhub < 5.5.0"],"patched":["jupyterhub 5.5.0"],"published":"2026-08-25","updated":"2026-09-10","sourceUpdated":"2026-09-10T12:25:49.028612030Z","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-p43p-whwx-q52h","references":[{"url":"https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-p43p-whwx-q52h"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54338"},{"url":"https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a"},{"url":"https://github.com/jupyterhub/jupyterhub"},{"url":"https://pypi.org/project/jupyterhub"},{"url":"https://github.com/advisories/GHSA-p43p-whwx-q52h"}],"tags":["osv","pip","nvd","ghsa"],"epss":0.00282,"epssPercentile":0.20991,"cwe":["CWE-400"],"ingestedAt":"2026-08-25T19:31:03.001Z","slug":"CVE-2026-54338","body":"## Overview\n\n### 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.\n\n## Affected packages\n\n- `jupyterhub < 5.5.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `jupyterhub 5.5.0`","depth":"sunlit","depthScore":29,"depthScoreParts":{"impact":29.2,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}