Rack QueryParser has an unsafe default allowing params_limit bypass via semicolon-separated parameters

{
  "id": "9b8480f6efe3081256ad78836dd690328bbeaeeb80f57ff93304650e01a635f3",
  "url": "https://osv.dev/vulnerability/CVE-2025-59830",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Rack QueryParser has an unsafe default allowing params_limit bypass via semicolon-separated parameters",
    "summary": "Rack is a modular Ruby web server interface. Prior to version 2.2.18, Rack::QueryParser enforces its params_limit only for parameters separated by &, while still splitting on both & and ;. As a result, attackers could use ; separators to bypass the parameter count limit and submit more parameters than intended. Applications or middleware that directly invoke Rack::QueryParser with its default configuration (no explicit delimiter) could be exposed to increased CPU and memory consumption. This can be abused as a limited denial-of-service vector. This issue has been patched in version 2.2.18.",
    "evidence": "osv:CVE-2025-59830",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2025-59830",
      "aliases": [
        "CVE-2025-59830",
        "GHSA-625h-95r8-8xpm"
      ],
      "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/rack/rack",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "0f76d43c0d5624bd0d325df4f0a63f5e1faa7254"
                },
                {
                  "fixed": "54e4ffdd5affebcb0c015cc6ae74635c0831ed71"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:rack:rack:*:*:*:*:*:ruby:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "2.2.18"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "54e4ffdd5affebcb0c015cc6ae74635c0831ed71"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v2.2.17",
            "v2.2.16",
            "v2.2.15",
            "v2.2.14",
            "v2.2.13",
            "v2.2.12",
            "v2.2.11",
            "v2.2.10",
            "v2.2.9",
            "v2.2.8",
            "v2.2.7",
            "v2.2.6.2",
            "v2.2.6.1",
            "v2.2.6",
            "v2.2.5",
            "2.2.4",
            "2.2.3",
            "v2.2.2",
            "v2.2.1",
            "2.2.0",
            "2.1.0",
            "2.0.1",
            "2.0.0",
            "2.0.0.rc1",
            "2.0.0.alpha",
            "1.6.0.beta",
            "1.5.1",
            "1.5.0",
            "1.4.1",
            "1.4.0",
            "1.3.0",
            "1.3.0.beta2",
            "1.3.0.beta",
            "1.0",
            "0.3",
            "0.2",
            "0.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2025-59830.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:44.390800545Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/59xxx/CVE-2025-59830.json",
        "https://github.com/rack/rack/security/advisories/GHSA-625h-95r8-8xpm",
        "https://nvd.nist.gov/vuln/detail/CVE-2025-59830",
        "https://github.com/rack/rack/commit/54e4ffdd5affebcb0c015cc6ae74635c0831ed71"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-400",
          "CWE-770"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/59xxx/CVE-2025-59830.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2025-59830",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 512444,
  "published_at": "2025-09-25T14:37:06.967+00:00"
}