ReDoS in fast-jwt when using RegExp in allowed* leading to CPU exhaustion during token verification

{
  "id": "16492ec2d0f2923864c42534a0d24e212118b68163714b11037a78ac34236dbd",
  "url": "https://osv.dev/vulnerability/CVE-2026-35041",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "ReDoS in fast-jwt when using RegExp in allowed* leading to CPU exhaustion during token verification",
    "summary": "fast-jwt provides fast JSON Web Token (JWT) implementation. From 5.0.0 to 6.2.0, a denial-of-service condition exists in fast-jwt when the allowedAud verification option is configured using a regular expression. Because the aud claim is attacker-controlled and the library evaluates it against the supplied RegExp, a crafted JWT can trigger catastrophic backtracking in the JavaScript regex engine, resulting in significant CPU consumption during verification. This vulnerability is fixed in 6.2.1.",
    "evidence": "osv:CVE-2026-35041",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-35041",
      "aliases": [
        "CVE-2026-35041",
        "GHSA-cjw9-ghj4-fwxf"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:H/UI:R/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/nearform/fast-jwt",
              "type": "GIT",
              "events": [
                {
                  "introduced": "72f91b547f5dca90715a70ff3cbaa042e40d8803"
                },
                {
                  "fixed": "6b13fe96614a38613d453f46ba0631c4cd09dcd8"
                },
                {
                  "fixed": "b0be0ca161593836a153d5180ca5358ad9b5de94"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:nearform:fast-jwt:*:*:*:*:*:node.js:*:*",
                    "range": [
                      {
                        "introduced": "5.0.0"
                      },
                      {
                        "fixed": "6.2.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "b0be0ca161593836a153d5180ca5358ad9b5de94"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "6b13fe96614a38613d453f46ba0631c4cd09dcd8"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v6.2.1"
                  }
                ]
              }
            }
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-35041.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:48.032848807Z",
      "provider": "osv",
      "references": [
        "https://github.com/nearform/fast-jwt/releases/tag/v6.2.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/35xxx/CVE-2026-35041.json",
        "https://github.com/nearform/fast-jwt/security/advisories/GHSA-cjw9-ghj4-fwxf",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-35041",
        "https://github.com/nearform/fast-jwt/commit/b0be0ca161593836a153d5180ca5358ad9b5de94",
        "https://github.com/nearform/fast-jwt/pull/595"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1333"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/35xxx/CVE-2026-35041.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-35041",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 515966,
  "published_at": "2026-04-09T14:55:22.807+00:00"
}