Socket.IO: Engine.IO Protocol Revision Mismatch DoS

{
  "id": "ee6f4c26cc558288a7a34ea1554f363377c901fcb37967efb10dacfdb80a3e38",
  "url": "https://osv.dev/vulnerability/CVE-2026-102599",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Socket.IO: Engine.IO Protocol Revision Mismatch DoS",
    "summary": "Socket.IO enables bidirectional and low-latency communication for every platform. From Engine.IO 6.6.0 until 6.6.10, a transport upgrade can independently derive an Engine.IO protocol revision from the upgrade request instead of enforcing the revision stored on the existing session. A malicious client can establish a valid session and send an upgrade request with a different or omitted EIO query parameter, attaching a transport with incompatible parser and heartbeat behavior. A crafted heartbeat packet can then trigger an uncaught exception and terminate the Node.js process, including when Engine.IO v3 compatibility is disabled because an omitted EIO value is interpreted as revision 3 on the affected path. This issue is fixed in Engine.IO 6.6.10.",
    "evidence": "osv:CVE-2026-102599",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-102599",
      "aliases": [
        "CVE-2026-102599",
        "GHSA-2gc4-cqfq-p2gv"
      ],
      "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/socketio/socket.io",
              "type": "GIT",
              "events": [
                {
                  "introduced": "791aa58f4c0a003335a945fdd704cb910bd35970"
                },
                {
                  "fixed": "64066c367386b3eb96677479a8978d6a8230c5ee"
                },
                {
                  "fixed": "86db1fc3db2cd315a065d64c4e48918ccf9b4729"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "6.6.0"
                      },
                      {
                        "fixed": "6.6.10"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "86db1fc3db2cd315a065d64c4e48918ccf9b4729"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "64066c367386b3eb96677479a8978d6a8230c5ee"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "engine.io@6.6.10"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-102599.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:51.965058441Z",
      "provider": "osv",
      "references": [
        "https://github.com/socketio/socket.io/releases/tag/engine.io@6.6.10",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102599.json",
        "https://github.com/socketio/socket.io/security/advisories/GHSA-2gc4-cqfq-p2gv",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-102599",
        "https://github.com/socketio/socket.io/commit/86db1fc3db2cd315a065d64c4e48918ccf9b4729"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-248"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/102xxx/CVE-2026-102599.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-102599",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 520919,
  "published_at": "2026-10-13T19:05:10.87+00:00"
}