CVE-2021-33318Public exploitNetwork attack vector

Remote validation bypass via malformed IP notation

Published May 16, 2022 · Updated Aug 3, 2024

Input validation in IpMatcher and WatsonWebserver through the affected versions allows remote attackers to bypass IP allowlists or denylists via malformed addresses and netmasks. Matcher accepts octal, hexadecimal, and other noncanonical IP representations without validating or normalizing them against stored networks, producing mismatches. Exploitation requires a network-facing application that relies on these checks and can lead to server-side request forgery, local or remote file access, or service interruption.

CVSS severity9.8
Critical
EPSS probability2.02%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Input validation in IpMatcher and WatsonWebserver through the affected versions allows remote attackers to bypass IP allowlists or denylists via malformed addresses and netmasks. Matcher accepts octal, hexadecimal, and other noncanonical IP representations without validating or normalizing them against stored networks, producing mismatches. Exploitation requires a network-facing application that relies on these checks and can lead to server-side request forgery, local or remote file access, or service interruption.

The record

CVE
CVE-2021-33318
Published
May 16, 2022
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-704
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 16, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P
9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-704Incorrect Type Conversion or Cast

Public exploit references

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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