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CVE-2026-55254

Status: AnalyzedMedium (6.5)—

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.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

Ncalc — Ncalc

CWEs

References

Raw JSON (NVD)

Show
{
  "id": "CVE-2026-55254",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-55254",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "none"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-07-20T18:06:03.191078Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 4.8,
          "attackVector": "ADJACENT_NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H",
          "integrityImpact": "NONE",
          "userInteraction": "REQUIRED",
          "attackComplexity": "HIGH",
          "availabilityImpact": "HIGH",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "NONE"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 1.2
      },
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
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          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
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          "confidentialityImpact": "NONE"
        },
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        "exploitabilityScore": 2.8
      }
    ]
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  "affected": [
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      "source": "security-advisories@github.com",
      "affectedData": [
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          "versions": [
            {
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              "version": "< 6.1.1"
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  "published": "2026-07-17T20:17:27.023",
  "references": [
    {
      "url": "https://github.com/ncalc/ncalc/commit/eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a",
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      "url": "https://github.com/ncalc/ncalc/pull/575",
      "tags": [
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        "Patch"
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      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/ncalc/ncalc/releases/tag/v6.1.1",
      "tags": [
        "Product",
        "Release Notes"
      ],
      "source": "security-advisories@github.com"
    },
    {
      "url": "https://github.com/ncalc/ncalc/security/advisories/GHSA-3w5p-95mh-gq75",
      "tags": [
        "Patch",
        "Vendor Advisory"
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      "source": "security-advisories@github.com"
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  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
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      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
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          "lang": "en",
          "value": "CWE-190"
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        {
          "lang": "en",
          "value": "CWE-770"
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  "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."
    }
  ],
  "lastModified": "2026-08-18T15:44:07.357",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
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              "vulnerable": true,
              "matchCriteriaId": "4324B778-60F1-4BA5-B868-F54B638D257E",
              "versionEndExcluding": "6.1.1"
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          "operator": "OR"
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  "sourceIdentifier": "security-advisories@github.com"
}