How severe is CVE-2021-33318?

CVE-2021-33318 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-33318 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-33318?

CVE-2021-33318 primarily affects Ipmatcher Project Ipmatcher. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-33318?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-33318 published?

CVE-2021-33318 was published on 2022-05-16 and last updated on 2026-06-17.

CVE-2021-33318

CVE-2021-33318 is a critical-severity vulnerability in Ipmatcher Project Ipmatcher with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-704.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 2% (77th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-704
Affected product: Ipmatcher Project Ipmatcher
Published: 2022-05-16
Last modified: 2026-06-17

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.

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.
How severe is CVE-2021-33318?: CVE-2021-33318 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-33318 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (77th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-33318?: CVE-2021-33318 primarily affects Ipmatcher Project Ipmatcher. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-33318?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-33318 published?: CVE-2021-33318 was published on 2022-05-16 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:ipmatcher_project:ipmatcher:*:*:*:*:*:*:*:*
cpe:2.3:a:watsonwebserver_project:watsonwebserver:*:*:*:*:*:*:*:*

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CVE-2011-2337 — Critical (CVSS 9.8): A wrong type is used for a return value from strlen in WebKit in Google Chrome before Blink M12 on 64-bit platforms.

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