MRSAM Net::CIDR up to 0.23 on Perl cidrvalidate type conversion

Summaryinfo

A vulnerability was found in MRSAM Net::CIDR up to 0.23 on Perl. It has been rated as critical. Impacted is the function cidrvalidate. The manipulation leads to type conversion. This vulnerability is traded as CVE-2021-4456. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in MRSAM Net::CIDR up to 0.23 on Perl and classified as critical. This issue affects the function cidrvalidate. The manipulation with an unknown input leads to a type conversion vulnerability. Using CWE to declare the problem leads to CWE-704. The product does not correctly convert an object, resource, or structure from one type to a different type. The impact remains unknown. The summary by CVE is:

Net::CIDR versions before 0.24 for Perl mishandle leading zeros in IP CIDR addresses, which may have unspecified impact. The functions `addr2cidr` and `cidrlookup` 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 `cidrvalidate` function. However, this mitigation is optional and not enforced by default. In practice, users may call `addr2cidr` or `cidrlookup` with untrusted input and without validation, incorrectly assuming that this is safe.

The advisory is shared at blog.urth.org. The identification of this vulnerability is CVE-2021-4456 since 05/19/2025. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 300179 (Linux Distros Unpatched Vulnerability : CVE-2021-4456), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 0.24 eliminates this vulnerability. Applying the patch e3648c6bc6bdd018f90cca4149c467017d42bd10 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (300179) and CERT Bund (WID-SEC-2026-0688). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

• cPanel cPanel/WHM

Productinfo

Vendor

• MRSAM

Name

• Net::CIDR

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5
• 0.6
• 0.7
• 0.8
• 0.9
• 0.10
• 0.11
• 0.12
• 0.13
• 0.14
• 0.15
• 0.16
• 0.17
• 0.18
• 0.19
• 0.20
• 0.21
• 0.22
• 0.23

License

• open-source

CPE 2.3info

• 🔒
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CPE 2.2info

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Entryinfo

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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