CVE-2021-47156Network attack vector

Access-control bypass via ambiguous octal IP parsing

Published Mar 18, 2024 · Updated Mar 27, 2025

Improper IP address validation in Net::IPAddress::Util before 5.000 allows remote attackers to bypass IP-based access controls. The IP constructor accepts dotted IPv4 octets with leading zeros and resolves them as octal values, so textual and effective addresses can differ. Exploitation requires an application to trust the parsed address for an IP-based authorization decision, enabling unauthorized data access or modification.

CVSS severity6.5
Medium
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper IP address validation in Net::IPAddress::Util before 5.000 allows remote attackers to bypass IP-based access controls. The IP constructor accepts dotted IPv4 octets with leading zeros and resolves them as octal values, so textual and effective addresses can differ. Exploitation requires an application to trust the parsed address for an IP-based authorization decision, enabling unauthorized data access or modification.

The record

CVE
CVE-2021-47156
Published
Mar 18, 2024
Updated
Mar 27, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-1287
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 18, 2024CVE publishedPublication date reported by the CVE source.
  2. Mar 27, 2025Record 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

6.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

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.

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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 exploitUnconfirmed

Weakness, pattern, technique

CWE-1287Improper Validation of Specified Type of Input

Public exploit references

No public exploit references are available in this record.

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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