multer vulnerable to Denial of Service via oversized array index in field names

{
  "id": "12d8f4abc2308578cc353bb0afb63a4ac61ba8a7f09c22790a7fecf301d0ae7d",
  "url": "https://osv.dev/vulnerability/CVE-2026-82333",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "multer vulnerable to Denial of Service via oversized array index in field names",
    "summary": "multer is a middleware for handling multipart/form-data in Node.js. A small multipart request with two specially crafted text field names can make multer's field parser synchronously iterate a maximum-length sparse array, blocking the event loop so the process cannot handle other requests. A large numeric array index in the first field allocates a maximum-length sparse array, and a second field with a non-numeric key then triggers a full-length iteration inside the append-field dependency. All versions before 2.3.0 are affected, and this is a remotely triggerable denial of service. multer 2.3.0 adds an opt-in fieldArrayIndexLimit option that rejects oversized array indexes. Upgrade to multer 2.3.0 and set limits.fieldArrayIndexLimit to the largest array index your application needs to remediate.",
    "evidence": "osv:CVE-2026-82333",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-82333",
      "aliases": [
        "CVE-2026-82333",
        "GHSA-535w-7cp7-47q4"
      ],
      "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/expressjs/multer",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "4e8edf50dbb5ddec213b6253642cbc08ce0225a7"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "2.3.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StandardRange"
                  },
                  {
                    "cpe": "cpe:2.3:a:expressjs:multer:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "2.3.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.2.0",
            "v2.1.1",
            "v2.1.0",
            "v2.0.2",
            "v2.0.1",
            "v2.0.0",
            "v1.4.5-lts.2",
            "v1.4.5-lts.1",
            "v1.4.4",
            "v1.4.4-lts.1",
            "v1.4.3",
            "v1.4.2",
            "v1.4.1",
            "v1.4.0",
            "v1.3.1",
            "v1.3.0",
            "v1.2.1",
            "v1.2.0",
            "v1.1.0",
            "v1.0.6",
            "v1.0.5",
            "v1.0.4",
            "v1.0.3",
            "v1.0.2",
            "v1.0.1",
            "v1.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-82333.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:21.617206936Z",
      "provider": "osv",
      "references": [
        "https://cna.openjsf.org/security-advisories.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82333.json",
        "https://github.com/expressjs/multer/security/advisories/GHSA-535w-7cp7-47q4",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-82333"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-400"
        ],
        "cna_assigner": "openjs",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82333.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-82333",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 487728,
  "published_at": "2026-08-28T20:12:21.355+00:00"
}