JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login

{
  "id": "41eeac5fc61d1139ab82a812f243adb19bd127322b0316e6c45684394f1b7f66",
  "url": "https://osv.dev/vulnerability/CVE-2026-54338",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login",
    "summary": "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.",
    "evidence": "osv:CVE-2026-54338",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-54338",
      "aliases": [
        "BIT-jupyterhub-2026-54338",
        "CVE-2026-54338",
        "GHSA-p43p-whwx-q52h",
        "PYSEC-2026-3853"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/jupyterhub/jupyterhub",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "97b3154610726b5b7d8768f1e89a4d910e002854"
                },
                {
                  "fixed": "d6dc595f84b7509969686da31d87d6d69e7fce0a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "5.5.0"
                      }
                    ],
                    "source": "DESCRIPTION"
                  },
                  {
                    "range": [
                      {
                        "fixed": "d6dc595f84b7509969686da31d87d6d69e7fce0a"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "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"
          }
        }
      ],
      "modified": "2026-10-28T02:30:26.850178353Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54338.json",
        "https://github.com/jupyterhub/jupyterhub/security/advisories/GHSA-p43p-whwx-q52h",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-54338",
        "https://github.com/jupyterhub/jupyterhub/commit/d6dc595f84b7509969686da31d87d6d69e7fce0a"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-400"
        ],
        "cna_assigner": "GitHub_M",
        "unresolved_ranges": [
          {
            "extracted_events": [
              {
                "range": [
                  {
                    "introduced": "< 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": "< 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."
                  }
                ],
                "source": "AFFECTED_FIELD",
                "strategy": "StandaloneSingleVersion"
              }
            ]
          }
        ],
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54338.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-54338",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 493390,
  "published_at": "2026-08-07T20:52:55.068+00:00"
}