{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "8.11.0"
              },
              {
                "fixed": "8.11.2"
              }
            ],
            "source": "AFFECTED_FIELD"
          },
          "events": [
            {
              "introduced": "6e48f4873a677ed6a13fa3e3571b032f00244bdf"
            },
            {
              "fixed": "7e016ad7e5bd6540170069a9a28b1e633b29664f"
            }
          ],
          "repo": "https://github.com/nodejs/undici",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-qq8j-7v2v-3rwp"
  ],
  "database_specific": {
    "cna_assigner": "openjs",
    "cwe_ids": [
      "CWE-248",
      "CWE-754"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109855.json"
  },
  "details": "undici is an HTTP client library for Node.js. In versions 8.11.0 and 8.11.1, its experimental WebSocket client, which is enabled by default when HTTP/2 is allowed, mishandles a failed WebSocket handshake over HTTP/2: the request is already marked completed, so the abort becomes a no-op and the underlying HTTP/2 stream is left open with no error listener. When a malicious server then destroys the connection, the orphaned stream emits an unhandled error and the Node.js process exits. A remote, unauthenticated server can therefore crash any client that opens a WebSocket to it over HTTP/2, resulting in a denial of service. The issue is fixed in undici 8.11.2, and users should upgrade to 8.11.2 or later. As a workaround, set allowH2 to false to disable HTTP/2 for WebSocket connections, or avoid opening WebSocket connections to untrusted servers.",
  "id": "CVE-2026-109855",
  "modified": "2026-10-16T02:31:15.669695961Z",
  "published": "2026-10-15T08:12:51.245Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://cna.openjsf.org/security-advisories.html"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109855.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/nodejs/undici/security/advisories/GHSA-qq8j-7v2v-3rwp"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-109855"
    }
  ],
  "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:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake"
}