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Fencer Vulns
medium 4.8

CVE-2026-55254 json

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

published 2026-06-18 4 mo ago modified 2026-08-18 2 mo ago also GHSA-3w5p-95mh-gq75 , EUVD-2026-45304

cvss
4.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 21%
public exploits
0
none known

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.

Patch / fix

  • nuget NCalc.Core 6.1.1
  • nuget NCalcSync 6.1.1
  • ncalc ncalc 6.1.1

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.29% chance of exploitation in the next 30 days, higher than 21% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 4.8 CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H
NVD 3.1 6.5 CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 4.8 CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
nuget NCalc.Core
<6.1.1
6.1.1
nuget NCalcSync
<6.1.1
6.1.1

Affected products

  • ncalc ncalc

Classification

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

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.