path-to-regexp vulnerable to Denial of Service via sequential optional groups

{
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "cveMetadata": {
    "cveId": "CVE-2026-4926",
    "assignerOrgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
    "assignerShortName": "openjs",
    "dateUpdated": "2026-03-26T18:59:38.000Z",
    "dateReserved": "2026-03-26T18:36:49.229Z",
    "datePublished": "2026-03-26T18:59:38.000Z",
    "state": "PUBLISHED"
  },
  "containers": {
    "cna": {
      "providerMetadata": {
        "orgId": "ce714d77-add3-4f53-aff5-83d477b104bb",
        "shortName": "openjs",
        "dateUpdated": "2026-03-26T18:59:38.000Z"
      },
      "title": "path-to-regexp vulnerable to Denial of Service via sequential optional groups",
      "descriptions": [
        {
          "lang": "en",
          "value": "Impact:\n\nA bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service.\n\nPatches:\n\nFixed in version 8.4.0.\n\nWorkarounds:\n\nLimit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns.",
          "supportingMedia": [
            {
              "type": "text/html",
              "base64": false,
              "value": "Impact:\n\nA bad regular expression is generated any time you have multiple sequential optional groups (curly brace syntax), such as `{a}{b}{c}:z`. The generated regex grows exponentially with the number of groups, causing denial of service.\n\nPatches:\n\nFixed in version 8.4.0.\n\nWorkarounds:\n\nLimit the number of sequential optional groups in route patterns. Avoid passing user-controlled input as route patterns."
            }
          ]
        }
      ],
      "affected": [
        {
          "vendor": "path-to-regexp",
          "product": "path-to-regexp",
          "defaultStatus": "unaffected",
          "versions": [
            {
              "version": "8.0.0",
              "status": "affected",
              "versionType": "semver",
              "lessThan": "8.4.0"
            },
            {
              "version": "8.4.0",
              "status": "unaffected",
              "versionType": "semver"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "CWE-400: Uncontrolled Resource Consumption",
              "cweId": "CWE-400",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "lang": "en",
              "description": "CWE-1333: Inefficient Regular Expression Complexity",
              "cweId": "CWE-1333",
              "type": "CWE"
            }
          ]
        }
      ],
      "references": [
        {
          "url": "https://cna.openjsf.org/security-advisories.html"
        }
      ],
      "metrics": [
        {
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ],
          "cvssV3_1": {
            "version": "3.1",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
            "baseScore": 7.5,
            "baseSeverity": "HIGH"
          }
        }
      ],
      "credits": [
        {
          "lang": "en",
          "value": "uug4na",
          "type": "reporter"
        },
        {
          "lang": "en",
          "value": "blakeembrey",
          "type": "remediation developer"
        },
        {
          "lang": "en",
          "value": "UlisesGascon",
          "type": "remediation reviewer"
        }
      ]
    }
  }
}