multer vulnerable to Denial of Service via deeply nested field names

{
  "id": "4f293b499cca39301cf2b1fe164cd258b8f7c3a054fb72c0d121a7755f23cfad",
  "url": "https://osv.dev/vulnerability/CVE-2026-5079",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "multer vulnerable to Denial of Service via deeply nested field names",
    "summary": "Impact: multer versions 1.0.0 through 2.1.1 and 3.0.0-alpha.1 are vulnerable to a Denial of Service via deeply nested field names in multipart form data. The append-field dependency parses bracket notation in field names with no limit on nesting depth, allowing an attacker to force allocation of deeply nested object structures that consume CPU and memory. A single HTTP request with a crafted multipart body is sufficient to exploit this. Patches: Users should upgrade to multer 2.2.0 (2.x line) or 3.0.0-alpha.2 (3.x prerelease) and configure the new limits.fieldNestingDepth option to the minimum depth their application requires. Workarounds: Set limits.fields to a reasonable value to reduce the number of fields an attacker can send per request. This does not fully mitigate the issue but limits the impact.",
    "evidence": "osv:CVE-2026-5079",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-5079",
      "aliases": [
        "CVE-2026-5079",
        "GHSA-72gw-mp4g-v24j"
      ],
      "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": "869e2138af1d2b9cf62b8abb95e5785aef007b4b"
                },
                {
                  "fixed": "2e2af08157c66cbbc76539ccbd8869097a0c8feb"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:expressjs:multer:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "1.0.0"
                      },
                      {
                        "fixed": "2.2.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "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-2026-5079.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.054283765Z",
      "provider": "osv",
      "references": [
        "https://cna.openjsf.org/security-advisories.html",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5079.json",
        "https://github.com/expressjs/multer/security/advisories/GHSA-72gw-mp4g-v24j",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-5079"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-400"
        ],
        "cna_assigner": "openjs",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/5xxx/CVE-2026-5079.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-5079",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 499881,
  "published_at": "2026-06-15T13:56:45.52+00:00"
}