CVE-2021-33318: Ipmatcher Project Ipmatcher

Critical severity, CVSS 9.8. EPSS: 2.1% chance of exploitation in the next 30 days.

An Input Validation Vulnerability exists in Joel Christner .NET C# packages WatsonWebserver, IpMatcher 1.0.4.1 and below (IpMatcher) and 4.1.3 and below (WatsonWebserver) due to insufficient validation of input IP addresses and netmasks against the internal Matcher list of IP addresses and subnets.

Affected products

• Ipmatcher Project Ipmatcher: up to and including 1.0.4.1
• Watsonwebserver Project Watsonwebserver: up to and including 4.1.3

Published 2022-05-16. Last modified 2026-06-17.