CVE-2021-47155
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThe Net::IPV4Addr module 0.10 for Perl does not properly consider extraneous zero characters in an IP address string, which (in some situations) allows attackers to bypass access control that is based on IP addresses.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceThe Net::IPV4Addr Perl module version 0.10 fails to properly validate IP addresses containing extraneous zero characters, allowing attackers to bypass IP-based access control restrictions in certain situations by presenting malformed IP strings that parse differently than expected.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Net::IPV4Addr installation statusRun 'perldoc Net::IPV4Addr' or 'perl -MNet::IPV4Addr -e 'print $Net::IPV4Addr::VERSION'' to see if the module is installed and obtain its version numberAffected if Module is installed and version is 0.10
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Confirm affected versionCompare the installed version to the known vulnerable version 0.10 - note that only version 0.10 is explicitly listed as affected in the CVE summaryAffected if Installed version is exactly 0.10
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Identify usage in access control logicSearch codebase for 'Net::IPV4Addr' references in permission checks, ACL evaluations, or IP-based filtering routines - the vulnerability only matters when this module is used to validate IPs for access controlAffected if Code uses Net::IPV4Addr to validate IP addresses for access control decisions
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Test malformed IP parsing behaviorPass IP strings with extraneous leading zeros (such as '00192.168.1.1' or '01.0.0.1') to Net::IPV4Addr::new and compare parsed result against expected value - the module may parse these differently than intendedAffected if Malformed IPs with leading zeros parse to a different IP address than their canonical form, or parsing behavior varies unexpectedly
User is affected if Net::IPV4Addr version 0.10 is installed and used to validate IP addresses for access control decisions, with the module accepting malformed IP strings containing extraneous zero characters that bypass intended restrictions.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpgrade to a patched version of Net::IPV4Addr or implement supplementary input validation/sanitization on IP addresses before using them in access control decisions.
- Consultation3.0 h
- Implementation6.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,224.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-47155 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-47155 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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