TI-2026-39927 Aliases CVE-2026-55254 GHSA-3w5p-95mh-gq75

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

LOW 29CWE-190Published 2026-07-17 · Updated 2026-07-20

Key facts

Attack vector: Adjacent network
Privileges required: None
User interaction: None
Attack complexity: Low
Impact type: Denial of service
Confidentiality · integrity · availability: None · None · High
Fix status: Fixed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and GitHub. Impact type from CWE-190 and the CVSS impact.

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.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV

EPSS 0.00292 21st percentileScored 2026-11-07

Fix Fixed ncalc (ncalc): 6.1.1NCalc.Core (NuGet): 6.1.1+1 more product

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation: None
Automatable: No
Technical impact: Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

Vendor	Product	Affected versions	Fixed in	Status	Source
ncalc	ncalc	before 6.1.1	6.1.1	Patch available	CNA
—	NCalc.Core (NuGet)	before 6.1.1	6.1.1	Patch available	GHSA-3w5p-95mh-gq75
—	NCalcSync (NuGet)	before 6.1.1	6.1.1	Patch available	GHSA-3w5p-95mh-gq75

ncalc Vendorncalc Affected before 6.1.1 Fixed in 6.1.1 Patch available CNA
NCalc.Core (NuGet) Vendor— Affected before 6.1.1 Fixed in 6.1.1 Patch available GHSA-3w5p-95mh-gq75
NCalcSync (NuGet) Vendor— Affected before 6.1.1 Fixed in 6.1.1 Patch available GHSA-3w5p-95mh-gq75

CPE configurations NVD · 1

CPE	Versions	Role	Vendor
cpe:2.3:a:ncalc:ncalc::::::::	before 6.1.1	Vulnerable	ncalc

cpe:2.3:a:ncalc:ncalc:*:*:*:*:*:*:*:* Versions before 6.1.1 Vulnerable ·ncalc

Remediation

Fix · CNA ncalc (ncalc) Fixed in 6.1.1
Fix · GHSA-3w5p-95mh-gq75 NCalc.Core (NuGet) Fixed in 6.1.1 Advisory →
Fix · GHSA-3w5p-95mh-gq75 NCalcSync (NuGet) Fixed in 6.1.1 Advisory →

Timeline

2026-10-02 Threatist record created from CVE-2026-55254
2026-10-03 Alias added: GHSA-3w5p-95mh-gq75

References

Patch 3

Other 2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences