CVE-2021-4456

MEDIUM EPSS 24.0%
Published Feb 27, 20264mo ago · Modified Jun 17, 20262w ago
6.5 CVSS 3.1
Medium
Find Similar
Published Feb 27, 2026 4mo ago
Last Modified Jun 17, 2026 2w ago

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.

CVSS Details

Base Score
6.5
Exploitability
3.9
Impact
2.5
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required None
User Interaction None
Scope Unchanged
Confidentiality Low
Integrity Low
Availability None

Threat Intelligence

EPSS Exploit Probability
24.0% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-704

Affected Products 1

VendorProductVersionRange
mrsamnet\\ <0.24

References 3

  • blog.urth.org https://blog.urth.org/2021/03/29/security-issues-in-perl-ip-address-distros/
    Third Party Advisory
  • github.com https://github.com/svarshavchik/Net-CIDR/commit/e3648c6bc6bdd018f90cca4149c467017d42bd10
    Patch
  • metacpan.org https://metacpan.org/dist/Net-CIDR/changes
    Release Notes

Remediation

  • github.com https://github.com/svarshavchik/Net-CIDR/commit/e3648c6bc6bdd018f90cca4149c467017d42bd10
    Patch