Application hang via overflowing factorial loop
Published Jul 17, 2026 · Updated Jul 17, 2026
Denial of service in NCalc before 6.1.1 allows context-dependent attackers to hang a host application via a crafted factorial expression. The Factorial path in src/NCalc.Core/Helpers/MathHelper.cs sends unchecked numeric operands into a multiplication loop whose counter can overflow instead of terminating. Reachability requires a host application to evaluate an attacker-influenced expression; the resulting CPU exhaustion hangs that application or its service.
Summary
What happened
Denial of service in NCalc before 6.1.1 allows context-dependent attackers to hang a host application via a crafted factorial expression. The Factorial path in src/NCalc.Core/Helpers/MathHelper.cs sends unchecked numeric operands into a multiplication loop whose counter can overflow instead of terminating. Reachability requires a host application to evaluate an attacker-influenced expression; the resulting CPU exhaustion hangs that application or its service.
The record
- CVE
- CVE-2026-55254
- Published
- Jul 17, 2026
- Updated
- Jul 17, 2026
- Vendor
- NCalc
- Product
- NCalc
- Classifications
- CWE-770, CWE-190, T1499.004
- Attack vector
- adjacent
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 17, 2026CVE publishedPublication date reported by the CVE source.
- Jul 17, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 6.1.1
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Published oversized-factorial trigger expressionsproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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