undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake

{
  "id": "0d1047eca3666161e32414c6063d1924bdebb0e01f04559c5ba2a7e7f666a99d",
  "url": "https://osv.dev/vulnerability/CVE-2026-109855",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake",
    "summary": "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.",
    "evidence": "osv:CVE-2026-109855",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-109855",
      "aliases": [
        "CVE-2026-109855",
        "GHSA-qq8j-7v2v-3rwp"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/nodejs/undici",
              "type": "GIT",
              "events": [
                {
                  "introduced": "6e48f4873a677ed6a13fa3e3571b032f00244bdf"
                },
                {
                  "fixed": "7e016ad7e5bd6540170069a9a28b1e633b29664f"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "8.11.0"
                      },
                      {
                        "fixed": "8.11.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "cpe": "cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "8.11.0"
                      },
                      {
                        "fixed": "8.11.2"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v8.11.1",
            "v8.11.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-109855.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:44.506969006Z",
      "provider": "osv",
      "references": [
        "https://cna.openjsf.org/security-advisories.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109855.json",
        "https://github.com/nodejs/undici/security/advisories/GHSA-qq8j-7v2v-3rwp",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-109855"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-248",
          "CWE-754"
        ],
        "cna_assigner": "openjs",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/109xxx/CVE-2026-109855.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-109855",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 512492,
  "published_at": "2026-10-15T08:12:51.245+00:00"
}