{"id":"CVE-2026-54338","aliases":["BIT-jupyterhub-2026-54338","DEBIAN-CVE-2026-54338","EUVD-2026-54678","GHSA-p43p-whwx-q52h","PYSEC-2026-3853","UBUNTU-CVE-2026-54338"],"status":"published","title":"JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","description":"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.","severity":{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00437,"percentile":0.38395,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-400"],"published":"2026-08-07T20:52:55Z","modified":"2026-11-11T02:48:53Z","fixes":[{"ecosystem":"PyPI","package":"jupyterhub","fixed_in":["5.5.0"],"sources":["ghsa","osv"]},{"ecosystem":"Bitnami","package":"jupyterhub","fixed_in":["5.5.0"],"sources":["osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"jupyterhub","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.5.0"}]}]},{"source":"osv","ecosystem":"Bitnami","package":"jupyterhub","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.5.0"}]}]},{"source":"osv","ecosystem":"Debian:12","package":"jupyterhub","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.0+ds1-1","5.0.0+ds1-1","5.0.0+ds1-2","5.0.0+ds1-3","5.0.0+ds1-4","5.2.1+ds1-1","5.2.1+ds1-2","5.2.1+ds1-3","5.2.1+ds1-4","5.2.1+ds1-5"]},{"source":"osv","ecosystem":"Debian:13","package":"jupyterhub","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.2.1+ds1-4","5.2.1+ds1-5"]},{"source":"osv","ecosystem":"Debian:14","package":"jupyterhub","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.2.1+ds1-4","5.2.1+ds1-5"]},{"source":"osv","ecosystem":"PyPI","package":"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"]},{"source":"osv","ecosystem":"PyPI","package":"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"]},{"source":"osv","ecosystem":"Ubuntu:22.04:LTS","package":"jupyterhub","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.0.0+ds1-1","2.0.0+ds1-2"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"jupyterhub","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["3.0.0+ds1-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"jupyterhub","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.2.1+ds1-4","5.2.1+ds1-5"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"jupyterhub","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.2.1+ds1-4"]}],"products":[{"vendor":"jupyterhub","product":"jupyterhub"}],"references":[{"url":"https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-p43p-whwx-q52h","tags":["x_refsource_CONFIRM","web","advisory","report"]},{"url":"https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a","tags":["x_refsource_MISC","web","fix","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54338","tags":["web","advisory"]},{"url":"https://github.com/advisories/GHSA-p43p-whwx-q52h","tags":["advisory"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54338.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-54338","tags":["advisory"]},{"url":"https://github.com/jupyterhub/jupyterhub","tags":["package"]},{"url":"https://pypi.org/project/jupyt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Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","description":"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.","status":"published","published":"2026-08-07T20:52:55.068Z","modified":"2026-08-11T01:15:53.601Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"cna"}],"cwes":["CWE-400"],"updated_at":"2026-11-02T13:37:58.613221Z"}],"euvd":[{"id":"EUVD-2026-54678","description":"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.","status":"published","published":"2026-08-07T20:52:55Z","modified":"2026-08-11T01:15:53Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T18:02:00.742322Z"}],"ghsa":[{"id":"GHSA-p43p-whwx-q52h","title":"JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","description":"### 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.","status":"published","published":"2026-08-25T19:29:19Z","modified":"2026-08-25T19:29:19Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-400"],"updated_at":"2026-11-02T14:41:05.994358Z"}],"nvd":[{"id":"CVE-2026-54338","description":"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.","status":"published","published":"2026-08-07T21:17:29.017Z","modified":"2026-09-09T20:58:37.713Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium","assessor":"secondary"}],"cwes":["CWE-400"],"updated_at":"2026-11-02T14:12:35.743275Z"}],"osv":[{"id":"CVE-2026-54338","title":"JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","description":"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.","status":"published","published":"2026-08-07T20:52:55.068Z","modified":"2026-11-11T10:47:32.948921723Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-400"],"updated_at":"2026-11-11T03:21:35.242594Z"},{"id":"DEBIAN-CVE-2026-54338","description":"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.","status":"published","published":"2026-08-07T21:17:29.017Z","modified":"2026-10-01T03:03:26.29857322Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T15:45:57.236551Z"},{"id":"GHSA-p43p-whwx-q52h","title":"JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","description":"### 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.","status":"published","published":"2026-08-25T19:29:19Z","modified":"2026-09-29T10:10:48.091771976Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"cwes":["CWE-400"],"updated_at":"2026-11-02T15:46:52.534897Z"},{"id":"PYSEC-2026-3853","title":"JupyterHub has Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","description":"### 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.","status":"published","published":"2026-09-10T09:44:57.193967Z","modified":"2026-09-29T10:10:48.091771976Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T15:52:57.255153Z"},{"id":"UBUNTU-CVE-2026-54338","description":"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.","status":"published","published":"2026-08-07T21:17:00Z","modified":"2026-10-17T12:58:35.443553283Z","cvss":[{"version":"3.1","score":5.3,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","level":"medium"}],"updated_at":"2026-11-02T16:56:41.382716Z"},{"id":"BIT-jupyterhub-2026-54338","title":"JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login","description":"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.","status":"published","published":"2026-09-29T08:44:40.894Z","modified":"2026-09-29T10:10:48.091771976Z","updated_at":"2026-11-02T15:28:31.782692Z"}]}}