CVE-1999-0045 is a high-severity vulnerability affecting multiple early versions of the Apache HTTP Server, specifically versions ranging from 0.8.11 through 2.0a. The vulnerability arises from the presence of the nph-test-cgi script, which allows an attacker to list arbitrary files on the web host. This script is a non-parsed header CGI test program that was included in early Apache distributions primarily for testing purposes. However, its presence in production environments exposes sensitive information by enabling unauthorized directory traversal or file enumeration attacks. The vulnerability is remotely exploitable without authentication (AV:N), requires low attack complexity (AC:L), and can compromise confidentiality, integrity, and availability (C:P/I:P/A:P) of the affected system. Although no official patch is available, modern Apache versions have removed or disabled this script by default, mitigating the risk. The vulnerability dates back to 1996 and is largely relevant to legacy systems still running these outdated Apache versions. Exploitation could allow attackers to gain insights into the file structure, potentially leading to further attacks such as information disclosure, privilege escalation, or denial of service.

For European organizations, the impact of this vulnerability primarily concerns legacy systems that have not been updated or patched for over two decades. If such systems are still operational and exposed to the internet, attackers could exploit this vulnerability to enumerate sensitive files, leading to information disclosure. This could compromise confidential data, intellectual property, or internal configurations. The ability to affect integrity and availability also raises concerns about potential system manipulation or service disruption. Given the age of the vulnerability, most modern European enterprises are unlikely to be directly affected; however, critical infrastructure or legacy industrial control systems in sectors like manufacturing, energy, or government that rely on outdated Apache versions could be at risk. Exploitation could facilitate lateral movement within networks or serve as a foothold for more sophisticated attacks, impacting business continuity and regulatory compliance under GDPR.

European organizations should immediately audit their web server environments to identify any instances of Apache HTTP Server versions listed as vulnerable (0.8.11 through 2.0a). Any presence of the nph-test-cgi script should be removed or disabled. Since no official patch exists for these versions, the primary mitigation is to upgrade to a supported, modern Apache version where this script is no longer included or enabled by default. Additionally, organizations should implement strict network segmentation and firewall rules to restrict access to web servers, especially legacy systems. Employing web application firewalls (WAFs) can help detect and block attempts to exploit this vulnerability. Regular vulnerability scanning and penetration testing should be conducted to ensure no residual exposure. For legacy systems that cannot be upgraded immediately, isolating them from public networks and applying compensating controls such as strict access controls and monitoring is critical.