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Vulnerabilities

Vulnerability · CVE-2021-4456

Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact.

Published Feb 27, 2026 · catalog updated Jun 17, 2026 · Net::CIDR versions before 0.24

Check if you run it

No confirmed exploitation is on record for CVE-2021-4456. EPSS is 0.34%. Act only if a listed version of Net::CIDR versions before 0.24 is installed.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Net::CIDR versions before 0.24).
  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium6.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.34%
Remediation
Advisory link
Affected products
cpe mrsam/net

Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact. The functions and may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses. The documentation advises validating untrusted CIDR strings with the function. However, this mitigation is optional and not enforced by default. In practice, users may call or with untrusted input and without validation, incorrectly assuming that this is safe.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe mrsam/net\

How to fix CVE-2021-4456

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2021-4456. EPSS is 0.34%. Act only if a listed version of Net::CIDR versions before 0.24 is installed.

Which versions are affected?

Compare what you have installed with \. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-704. EPSS 0.34%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Feb 27, 2026 · NIST NVD

    Detected

    Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact. The functions and may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses. The documentation advises validating untrusted C

  2. Jun 17, 2026 · NIST NVD

    Updated

    Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact. The functions and may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In some cases an attacker may be able to leverage this to bypass access controls based on IP addresses. The documentation advises validating untrusted C

Sources

  • CVE.orgVulnerability recordCVE-2021-4456

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2021-4456

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2021-4456

    Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact. The functions and may return leading zeros in a CIDR string, which may in turn be parsed as octal numbers by subsequent users. In som

    nvd.nist.gov

References

Freshness

Last verified in this catalog Oct 16, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.