Vulnerability in NCalc.Core (CVE-2026-55254)
Summary
Vulnerability in NCalc.Core (CVE-2026-55254). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 6.1.1 or later.
Original description
The description as published by the source.
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.
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-55254 has been found in NCalc.Core.
Risk of unauthorized operations or information disclosure. CVSS score: 4.8/10.
What to do: upgrade NCalc.Core to 6.1.1 or later.
If unsure, ask your IT team or search "NCalc.Core CVE-2026-55254" on the vendor's site.
CVE-2026-55254 (NCalc.Core) — CWE-190 / CVSS v3 4.8
Attack vector: adjacent-network / unauthenticated
Patched: 6.1.1 — apply immediately
Workaround: * Do not evaluate expressions originating from untrusted users.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-190) exists in NCalc.Core.
Check the vendor advisory for the affected versions of NCalc.Core.
Severity: Medium (CVSS 4.8/10). Risk of unauthorized operations or information disclosure.
Update to 6.1.1.
Workaround: * Do not evaluate expressions originating from untrusted users.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'NCalc.Core' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'NCalc.Core' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
NCalc.Coreを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
* Do not evaluate expressions originating from untrusted users.パッチが適用されるまでの応急処置として、* Do not evaluate expressions originating from untrusted users. を実施。回避策の副作用 (機能低下) を確認した上で。
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3Apply patch patch
Upgrade NCalc.Core to 6.1.1ステージング環境で 6.1.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- patch github.com
- web github.com
- web github.com