NCalc: Denial of Service via Unbounded and Non-Terminating Factorial Evaluation

{
  "id": "95d847d0c03a308cd5a868ee1f22da07243a760f3978a01c782f078c496283a8",
  "url": "https://osv.dev/vulnerability/CVE-2026-55254",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "NCalc: Denial of Service via Unbounded and Non-Terminating Factorial Evaluation",
    "summary": "NCalc is a fast, lightweight expression evaluator for .NET. Prior to 6.1.1, the factorial operator implementation in src/NCalc.Core/Helpers/MathHelper.cs permits specially crafted expressions with extremely large factorial operands, causing excessive CPU consumption or a non-terminating loop due to integer overflow in the factorial calculation logic when applications evaluate untrusted expressions. This issue is fixed in version 6.1.1.",
    "evidence": "osv:CVE-2026-55254",
    "products": [],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-55254",
      "aliases": [
        "CVE-2026-55254",
        "GHSA-3w5p-95mh-gq75"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/ncalc/ncalc",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "e885002a859c72eaf00b16a92d239960d289742f"
                },
                {
                  "fixed": "eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "cpe": "cpe:2.3:a:ncalc:ncalc:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "6.1.1"
                      }
                    ],
                    "source": "CPE_RANGE"
                  },
                  {
                    "range": [
                      {
                        "fixed": "eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  },
                  {
                    "range": [
                      {
                        "fixed": "e885002a859c72eaf00b16a92d239960d289742f"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "v6.1.1"
                  }
                ]
              }
            }
          ],
          "versions": [
            "v5.10.0",
            "v5.2.5",
            "v5.2.3",
            "5.2.1",
            "v4.2.0",
            "v4.0.0",
            "v3.13.1",
            "v2.0.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55254.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:33.271316214Z",
      "provider": "osv",
      "references": [
        "https://github.com/ncalc/ncalc/releases/tag/v6.1.1",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55254.json",
        "https://github.com/ncalc/ncalc/security/advisories/GHSA-3w5p-95mh-gq75",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-55254",
        "https://github.com/ncalc/ncalc/commit/eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a",
        "https://github.com/ncalc/ncalc/pull/575"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-190",
          "CWE-770"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55254.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-55254",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 500352,
  "published_at": "2026-07-17T19:55:16.728+00:00"
}