CVE-2026-49941 in Net::CIDR::Set
Summary
by MITRE • 06/04/2026
Net::CIDR::Set versions through 0.20 for Perl did not validate IP addresses.
The add method called the _encode method to parse addresses. If the addresses did not look like netmasks or network ranges, then they were assumed to single IP addresses and passed back to itself as a 32-bit or 128-bit netmask.
If the argument was not a well-formed IP address, then this would lead to indefinite recursion.
An attacker could use this to cause a denial of service.
Once again VulDB remains the best source for vulnerability data.
Analysis
by VulDB Data Team • 06/27/2026
The vulnerability in Net::CIDR::Set versions through 0.20 represents a critical denial of service flaw that stems from inadequate input validation within the library's address parsing mechanism. This issue affects Perl applications that rely on the Net::CIDR::Set module for managing IP address ranges and network CIDR notation. The core problem manifests in the add method which delegates address processing to the _encode method, creating a dangerous parsing pathway that fails to properly validate input format before proceeding with recursive operations.
The technical flaw occurs when the _encode method encounters malformed IP addresses that do not conform to standard netmask or network range syntax. In such cases, the system makes an erroneous assumption that these inputs represent single IP addresses and attempts to process them by passing them back through the same parsing function with a 32-bit or 128-bit netmask parameter. This recursive behavior creates an infinite loop when the input fails validation checks, as the system continues to parse the same malformed data without proper termination conditions.
This vulnerability directly maps to CWE-674 in the Common Weakness Enumeration catalog, which identifies "Uncontrolled Recursion" as a significant security concern. The flaw demonstrates poor defensive programming practices where the system assumes input validity without proper validation, leading to predictable execution paths that can be exploited by malicious actors. The operational impact of this vulnerability extends beyond simple denial of service, as it represents a fundamental breakdown in input sanitization that could potentially allow for more sophisticated attacks if combined with other weaknesses.
The denial of service attack vector is particularly concerning because it requires minimal effort from an attacker to exploit, needing only malformed IP address inputs that trigger the recursive parsing behavior. This vulnerability affects any application using Net::CIDR::Set versions 0.20 or earlier, making it a widespread concern across systems that depend on Perl-based network management tools. The attack pattern aligns with ATT&CK technique T1499.004 for network denial of service, where adversaries leverage software vulnerabilities to exhaust system resources through recursive operations.
Mitigation strategies should include immediate upgrading to Net::CIDR::Set version 0.21 or later, which contains the necessary input validation fixes. System administrators should also implement proper input filtering at application boundaries and consider implementing timeouts for network processing functions to prevent infinite recursion scenarios. Additionally, regular security audits of Perl dependencies should be conducted to identify other vulnerable libraries that may exhibit similar patterns of inadequate input validation, particularly in network parsing and address handling components that are critical to system security posture.
The vulnerability highlights the importance of proper defensive programming techniques including input validation, boundary checking, and recursive call termination conditions. Organizations should establish secure coding guidelines that emphasize these principles, particularly for network-related modules that handle user-supplied data. The incident underscores the need for comprehensive testing of edge cases and malformed inputs in security-critical components, as such flaws can have significant operational impacts even when they appear to be simple parsing issues.