CVE-2026-55254 (GCVE-0-2026-55254)

Vulnerability from cvelistv5 – Published: 2026-07-17 19:55 – Updated: 2026-07-17 19:55
VLAI
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.
Severity
4.8 (Medium)
CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H
CWE
  • CWE-770 - Allocation of Resources Without Limits or Throttling
  • CWE-190 - Integer Overflow or Wraparound
Assigner
References
Impacted products
Vendor Product Version
ncalc ncalc Affected: < 6.1.1
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{
  "containers": {
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        {
          "product": "ncalc",
          "vendor": "ncalc",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 6.1.1"
            }
          ]
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      ],
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        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "ADJACENT_NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 4.8,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "REQUIRED",
            "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H",
            "version": "3.1"
          }
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      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-770",
              "description": "CWE-770: Allocation of Resources Without Limits or Throttling",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-190",
              "description": "CWE-190: Integer Overflow or Wraparound",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-17T19:55:16.728Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/ncalc/ncalc/security/advisories/GHSA-3w5p-95mh-gq75",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/ncalc/ncalc/security/advisories/GHSA-3w5p-95mh-gq75"
        },
        {
          "name": "https://github.com/ncalc/ncalc/pull/575",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/ncalc/ncalc/pull/575"
        },
        {
          "name": "https://github.com/ncalc/ncalc/commit/eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/ncalc/ncalc/commit/eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a"
        },
        {
          "name": "https://github.com/ncalc/ncalc/releases/tag/v6.1.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/ncalc/ncalc/releases/tag/v6.1.1"
        }
      ],
      "source": {
        "advisory": "GHSA-3w5p-95mh-gq75",
        "discovery": "UNKNOWN"
      },
      "title": "NCalc: Denial of Service via Unbounded and Non-Terminating Factorial Evaluation"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-55254",
    "datePublished": "2026-07-17T19:55:16.728Z",
    "dateReserved": "2026-06-16T16:44:00.625Z",
    "dateUpdated": "2026-07-17T19:55:16.728Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-55254\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-07-17T20:17:27.023\",\"lastModified\":\"2026-07-17T20:17:27.023\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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.\"}],\"affected\":[{\"source\":\"security-advisories@github.com\",\"affectedData\":[{\"vendor\":\"ncalc\",\"product\":\"ncalc\",\"versions\":[{\"version\":\"\u003c 6.1.1\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H\",\"baseScore\":4.8,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"ADJACENT_NETWORK\",\"attackComplexity\":\"HIGH\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"REQUIRED\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.2,\"impactScore\":3.6}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-190\"},{\"lang\":\"en\",\"value\":\"CWE-770\"}]}],\"references\":[{\"url\":\"https://github.com/ncalc/ncalc/commit/eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ncalc/ncalc/pull/575\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ncalc/ncalc/releases/tag/v6.1.1\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/ncalc/ncalc/security/advisories/GHSA-3w5p-95mh-gq75\",\"source\":\"security-advisories@github.com\"}]}}"
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.