Checkmate: Regular Expression Denial of Service (ReDoS) via User-Controlled Regex in Monitor Advanced Matching

{
  "id": "385e49ef6dc1fba41e23f039c09a98ef91a008ce67104e9fbc8ed5df51e93b3d",
  "url": "https://osv.dev/vulnerability/CVE-2026-70656",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Checkmate: Regular Expression Denial of Service (ReDoS) via User-Controlled Regex in Monitor Advanced Matching",
    "summary": "Checkmate is an open-source, self-hosted tool designed to track and monitor server hardware, uptime, response times, and incidents in real-time with beautiful visualizations. From 3.5.1 until 3.9.2, an authenticated admin or superadmin can set matchMethod to regex and place a malicious expression in the expectedValue field for advanced HTTP monitor matching. server/src/api/validation/monitorValidation.ts accepts the expression, and server/src/service/network/AdvancedMatcher.ts synchronously evaluates it against an attacker-controlled HTTP response body on the Node.js main event loop without a timeout or worker isolation, allowing catastrophic backtracking to freeze API endpoints, monitor checks, and WebSocket connections for all users. This issue is fixed in version 3.9.2.",
    "evidence": "osv:CVE-2026-70656",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-70656",
      "aliases": [
        "CVE-2026-70656",
        "GHSA-4c6j-p2cv-wf56"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/bluewave-labs/checkmate",
              "type": "GIT",
              "events": [
                {
                  "introduced": "c2170267e8d4653e04040f40f220966208f8dc21"
                },
                {
                  "fixed": "d368ec5bd7af1cd81628c47a89d1d830cd415590"
                },
                {
                  "fixed": "0df71d6356c87c747e0b796b0c34e33f2a5203fa"
                },
                {
                  "fixed": "adba25269c455878bf8065bc28cfe5d74e58692f"
                },
                {
                  "fixed": "d5ec2936ad77ab773529057b442a6eb55dd578eb"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "3.5.1"
                      },
                      {
                        "fixed": "3.9.2"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "0df71d6356c87c747e0b796b0c34e33f2a5203fa"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "adba25269c455878bf8065bc28cfe5d74e58692f"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "d5ec2936ad77ab773529057b442a6eb55dd578eb"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "d368ec5bd7af1cd81628c47a89d1d830cd415590"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v3.9.2"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v3.9.1",
            "v3.7.1",
            "v3.6.1",
            "v3.5.1"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-70656.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:23.189644713Z",
      "provider": "osv",
      "references": [
        "https://github.com/bluewave-labs/Checkmate/releases/tag/v3.9.2",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/70xxx/CVE-2026-70656.json",
        "https://github.com/bluewave-labs/Checkmate/security/advisories/GHSA-4c6j-p2cv-wf56",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-70656",
        "https://github.com/bluewave-labs/Checkmate/commit/0df71d6356c87c747e0b796b0c34e33f2a5203fa",
        "https://github.com/bluewave-labs/Checkmate/commit/adba25269c455878bf8065bc28cfe5d74e58692f",
        "https://github.com/bluewave-labs/Checkmate/commit/d5ec2936ad77ab773529057b442a6eb55dd578eb"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-1333"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/70xxx/CVE-2026-70656.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-70656",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 489641,
  "published_at": "2026-08-21T17:59:28.639+00:00"
}