CVE-2021-4456

6.5 MEDIUM
Published: February 27, 2026 Modified: March 03, 2026
View on NVD

Description

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.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros/
Source: 9b29abf9-4ab0-4765-b253-1875cd9b441e
Third Party Advisory
https://metacpan.org/dist/Net-CIDR/changes
Source: 9b29abf9-4ab0-4765-b253-1875cd9b441e
Release Notes

3 reference(s) from NVD

Quick Stats

CVSS v3 Score
6.5 / 10.0
EPSS (Exploit Probability)
0.1%
20th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

mrsam