{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "source": "REFERENCES"
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "d6dc595f84b7509969686da31d87d6d69e7fce0a"
            }
          ],
          "repo": "https://github.com/jupyterhub/jupyterhub",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-p43p-whwx-q52h"
  ],
  "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": [
      {
        "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."
          }
        ],
        "source": "AFFECTED_FIELD"
      }
    ]
  },
  "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.",
  "id": "CVE-2026-54338",
  "modified": "2026-08-12T03:51:29.896100389Z",
  "published": "2026-08-07T20:52:55.068Z",
  "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"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "JupyterHub: Unauthenticated Denial of Service via Unbounded Username Logging on Failed Login"
}