Integer overflow in Ncalc
CVE-2026-55254
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.
Vulnerability class: Integer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:A/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.003 (20.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 20th percentile — 20.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.003 · change: +0.001
Affected products
- Ncalc — versions < 6.1.1
Weakness classification (CWE)
References
- github.com/ncalc/ncalc/commit/eeb6155ee1899b1fdf2cda3da35a4f0ca93ffd6a (Patch)
- github.com/ncalc/ncalc/pull/575 (Patch, Issue Tracking)
- github.com/ncalc/ncalc/releases/tag/v6.1.1 (Product, Release Notes)
- github.com/ncalc/ncalc/security/advisories/GHSA-3w5p-95mh-gq75 (Patch, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-55254?
- CVE-2026-55254 is a medium-severity vulnerability in Ncalc, classified under Integer Overflow or Wraparound. CVSS score: 4.8/10. Published 2026-07-17.
- How severe is CVE-2026-55254?
- Medium severity. CVSS v3 base score is 4.8 out of 10.