CVE-2000-0432 is a high-severity remote command execution vulnerability affecting version 2.2 of the calendar.pl and calendar_admin.pl scripts developed by Matt Kruse. These scripts are web-based calendar applications written in Perl, commonly used in the late 1990s and early 2000s to provide calendar functionality on websites. The vulnerability arises because the scripts improperly handle user-supplied input that is passed to shell commands without adequate sanitization or escaping of shell metacharacters. This flaw allows remote attackers to inject arbitrary shell commands by embedding metacharacters in input parameters, which the scripts then execute on the underlying server. Exploitation does not require authentication, and the attack can be performed over the network (AV:N), with low attack complexity (AC:L). Successful exploitation compromises confidentiality, integrity, and availability by allowing attackers to execute arbitrary commands, potentially leading to data theft, data modification, or service disruption. Despite the age of this vulnerability and the lack of known exploits in the wild, the absence of an available patch means vulnerable systems remain exposed if still in use. The CVSS base score is 7.5, reflecting the high impact and ease of exploitation. Given the nature of the vulnerability, it is critical for organizations still running these legacy scripts to take immediate action to mitigate risk.

For European organizations, the impact of this vulnerability can be significant if legacy web applications using Matt Kruse's calendar scripts are still operational. Successful exploitation could lead to full system compromise, allowing attackers to steal sensitive data, modify or delete information, or disrupt services. This is particularly concerning for organizations in sectors with strict data protection regulations such as finance, healthcare, and government, where data breaches can result in severe legal and reputational consequences. Additionally, compromised servers could be used as pivot points for further attacks within the network or as part of botnets, increasing the overall risk landscape. Although the scripts are outdated, some smaller organizations or legacy systems may still rely on them, making targeted attacks plausible. The lack of patches exacerbates the risk, as organizations must rely on alternative mitigation strategies. The vulnerability’s remote and unauthenticated nature increases the threat level, as attackers do not need prior access or credentials to exploit it.

Since no official patch is available for this vulnerability, European organizations should prioritize the following specific mitigation steps: 1) Immediately identify and inventory any instances of Matt Kruse's calendar.pl or calendar_admin.pl scripts version 2.2 or earlier within their environments. 2) Remove or disable these scripts entirely, replacing them with modern, actively maintained calendar solutions that follow secure coding practices. 3) If removal is not immediately feasible, implement strict input validation and sanitization at the web server or application firewall level to block shell metacharacters and suspicious input patterns targeting these scripts. 4) Employ web application firewalls (WAFs) with custom rules designed to detect and block exploitation attempts targeting this vulnerability. 5) Restrict web server permissions to limit the execution context of these scripts, minimizing potential damage from command execution. 6) Monitor web server logs and network traffic for unusual activity indicative of exploitation attempts, such as unexpected command execution or anomalous input parameters. 7) Educate IT and security teams about the risks associated with legacy scripts and the importance of timely software updates and replacements. These targeted actions go beyond generic advice by focusing on legacy script identification, replacement, and compensating controls to mitigate the absence of patches.