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No exploitation reportedFix available

CVE-2021-33318

No exploitation reported by the sources we read.

  • Published2022-05-16
  • Fixed in1.0.4.2
  • WeaknessCWE-704

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2022-05-1616:15CVE publishedNVD

Versions per branch

OSV · NVD
IpMatcher
BranchAffectedFixed in
1.0< 1.0.4.21.0.4.2
Ipmatcher project ipmatcher
BranchAffectedFixed in
1.0≤ 1.0.4.1no fix published
Watsonwebserver project watsonwebserver
BranchAffectedFixed in
4.1≤ 4.1.3no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update IpMatcher to 1.0.4.2

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • NVDCVSS 3.19.8read 2026-10-23
  • NVDCVSS 2.07.5read 2026-10-23
  • NVDweakness (CWE)CWE-704read 2026-10-23
  • FIRST EPSSEPSS score2.1 %2026-11-08
  • OSVaffected packages—
  • GitHub AdvisoriesadvisoryCRITICAL2022-05-25

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2022-05-16
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-qj93-37f5-mr29

Frequently asked questions

What is CVE-2021-33318?

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.

Is CVE-2021-33318 actively exploited?

Active exploitation of CVE-2021-33318 has not been confirmed. Its EPSS score was 2.1% on 2026-11-08, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-33318?

CVE-2021-33318 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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