CVE-2021-29424: The Net::Netmask module before 2.0000 for Perl does not properly consider extraneous zero characters at the be

Q: How do I fix CVE-2021-29424?

\: upgrade to 2.0000; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-29424 being exploited?

CVE-2021-29424 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-29424 affect?

CVE-2021-29424 affects \, fedora. Severity is high (CVSS 7.5). 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 addresse

Q: How urgent is CVE-2021-29424?

Priority 56/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADEMITIGATE

CVE-2021-29424 is a high-severity flaw (CVSS 7.5) affecting \, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.8% (top 22%)
CISA exploited list	No
Weakness	CWE-704
Published	2021-04-06
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: fedoraproject · net\

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-04-06 16:15 UTCPublished CVE record published
2026-06-17 03:47 UTCUpdated Record last modified

net\ \ UPGRADE

Affected: < 2.0000

Fixed in: 2.0000

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy || rpm -q || --version

2. UPGRADE to 2.0000 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 32 · 33 · 34

Fixed in: no fixed release known

Safe to downgrade to: a release before 32

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-29424?

\: upgrade to 2.0000; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-29424 being exploited?

CVE-2021-29424 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-29424 affect?

CVE-2021-29424 affects \, fedora. Severity is high (CVSS 7.5). 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 addresse

How urgent is CVE-2021-29424?

Priority 56/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

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References

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