Vulnerability-Lookup

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

Vulnerability from cvelistv5 – Published: 2026-07-17 19:55 – Updated: 2026-07-20 18:07

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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling
CWE-190 - Integer Overflow or Wraparound

Assigner

GitHub_M

References

4 references

URL	Tags
https://github.com/ncalc/ncalc/security/advisorie…	x_refsource_CONFIRM
https://github.com/ncalc/ncalc/pull/575	x_refsource_MISC
https://github.com/ncalc/ncalc/commit/eeb6155ee18…	x_refsource_MISC
https://github.com/ncalc/ncalc/releases/tag/v6.1.1	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
ncalc	ncalc	Affected: < 6.1.1

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-55254

Vulnerability from fkie_nvd - Published: 2026-07-17 20:17 - Updated: 2026-07-20 19:17

Severity

4.8 (Medium) - CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/ncalc/ncalc/commit/eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a
	security-advisories@github.com	https://github.com/ncalc/ncalc/pull/575
	security-advisories@github.com	https://github.com/ncalc/ncalc/releases/tag/v6.1.1
	security-advisories@github.com	https://github.com/ncalc/ncalc/security/advisories/GHSA-3w5p-95mh-gq75

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "ncalc",
          "vendor": "ncalc",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 6.1.1"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "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."
    }
  ],
  "id": "CVE-2026-55254",
  "lastModified": "2026-07-20T19:17:26.097",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
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          "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"
        },
        "exploitabilityScore": 1.2,
        "impactScore": 3.6,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
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    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
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          "options": [
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            }
          ],
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          "timestamp": "2026-07-20T18:06:03.191078Z",
          "version": "2.0.3"
        }
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  "published": "2026-07-17T20:17:27.023",
  "references": [
    {
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      "url": "https://github.com/ncalc/ncalc/commit/eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a"
    },
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      "source": "security-advisories@github.com",
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GHSA-3W5P-95MH-GQ75

Vulnerability from github – Published: 2026-06-18 13:05 – Updated: 2026-06-18 13:05

Summary

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

Details

Impact

A denial-of-service (DoS) vulnerability exists in the factorial operator implementation of NCalc. Specially crafted expressions containing extremely large factorial operands can trigger excessive CPU consumption or cause evaluation to enter a non-terminating loop due to integer overflow in the factorial calculation logic.

Applications that evaluate untrusted expressions using affected versions of NCalc may be vulnerable to resource exhaustion, potentially resulting in service disruption or application unresponsiveness.

This issue can be triggered with expressions such as:

99999999999999!
9223372036854775807!
1.5e16!

Patches

The vulnerability has been fixed by adding bounds validation for factorial operands and rejecting unsupported values before evaluation.

Users should upgrade to the first release containing the fix from pull request #575. (v6.1.1+)

Workarounds

If upgrading is not immediately possible:

Do not evaluate expressions originating from untrusted users.
Validate or sanitize expressions before evaluation and reject factorial operations on large values.
Implement execution time limits, request timeouts, or cancellation mechanisms around expression evaluation.

These mitigations may reduce exposure but do not fully address the underlying vulnerability.

Severity

4.8 (Medium)


                  
                    CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "NCalc.Core"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "NCalcSync"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "6.1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55254"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-190",
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-18T13:05:37Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nA denial-of-service (DoS) vulnerability exists in the factorial operator implementation of NCalc. Specially crafted expressions containing extremely large factorial operands can trigger excessive CPU consumption or cause evaluation to enter a non-terminating loop due to integer overflow in the factorial calculation logic.\n\nApplications that evaluate untrusted expressions using affected versions of NCalc may be vulnerable to resource exhaustion, potentially resulting in service disruption or application unresponsiveness.\n\nThis issue can be triggered with expressions such as:\n\n```text\n99999999999999!\n9223372036854775807!\n1.5e16!\n```\n\n### Patches\n\nThe vulnerability has been fixed by adding bounds validation for factorial operands and rejecting unsupported values before evaluation.\n\nUsers should upgrade to the first release containing the fix from pull request #575. (**v6.1.1+**)\n\n### Workarounds\n\nIf upgrading is not immediately possible:\n\n* Do not evaluate expressions originating from untrusted users.\n* Validate or sanitize expressions before evaluation and reject factorial operations on large values.\n* Implement execution time limits, request timeouts, or cancellation mechanisms around expression evaluation.\n\nThese mitigations may reduce exposure but do not fully address the underlying vulnerability.",
  "id": "GHSA-3w5p-95mh-gq75",
  "modified": "2026-06-18T13:05:37Z",
  "published": "2026-06-18T13:05:37Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/ncalc/ncalc/security/advisories/GHSA-3w5p-95mh-gq75"
    },
    {
      "type": "WEB",
      "url": "https://github.com/ncalc/ncalc/pull/575"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/ncalc/ncalc"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "NCalc: Denial of Service via Unbounded and Non-Terminating Factorial Evaluation"
}

Sightings

Author	Source	Type	Date	Other

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

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

FKIE_CVE-2026-55254

GHSA-3W5P-95MH-GQ75

Impact

Patches

Workarounds

Tags

Sightings

Nomenclature