CVE-1999-0738 is a vulnerability found in Microsoft Internet Information Server (IIS) version 4.0 and Site Server, specifically involving the code.asp sample file. This vulnerability allows remote attackers to read arbitrary files on the affected server without authentication. The issue arises because the code.asp sample file, which is included by default in these IIS installations, does not properly restrict access to sensitive files. An attacker can craft a specially formed HTTP request to the server that leverages this sample file to read contents of files outside the intended directory scope. This can lead to unauthorized disclosure of sensitive information such as configuration files, source code, or other data stored on the web server. The vulnerability is remotely exploitable over the network without requiring any user interaction or authentication, making it a significant risk for exposed IIS 4.0 servers. The CVSS v2 base score is 5.0 (medium severity), reflecting that the vulnerability impacts confidentiality only, with no impact on integrity or availability. Microsoft has released a security bulletin (MS99-013) providing patches and guidance to remediate this issue. Although no known exploits have been reported in the wild, the vulnerability's nature and ease of exploitation make it a notable risk for legacy IIS 4.0 deployments that remain unpatched.

For European organizations still running legacy IIS 4.0 servers, this vulnerability could lead to unauthorized disclosure of sensitive information hosted on their web servers. This includes internal configuration files, user data, or proprietary application code, which could be leveraged for further attacks such as privilege escalation or lateral movement. While IIS 4.0 is an outdated product and not commonly used in modern environments, some legacy systems in critical infrastructure, government, or industrial sectors may still rely on it. The exposure of sensitive files could result in reputational damage, regulatory non-compliance (e.g., GDPR concerns due to data leakage), and potential operational disruptions if attackers gain insights into system configurations. Given the vulnerability requires no authentication and can be exploited remotely, any IIS 4.0 server exposed to the internet or accessible within internal networks is at risk. However, the lack of known active exploitation reduces immediate threat levels, though the risk remains for unpatched legacy systems.

European organizations should prioritize the following specific mitigation steps: 1) Identify and inventory all IIS 4.0 servers and Site Server installations within their environment, including those in legacy or isolated networks. 2) Apply the official Microsoft patch provided in security bulletin MS99-013 immediately to remediate the vulnerability. 3) If patching is not feasible due to legacy dependencies, remove or restrict access to the code.asp sample file to prevent exploitation. This can be done by deleting the file or configuring IIS to deny access to it. 4) Implement network-level controls such as firewall rules or segmentation to limit external and internal access to legacy IIS servers. 5) Monitor web server logs for suspicious requests targeting code.asp or attempts to read arbitrary files. 6) Plan and execute an upgrade strategy to migrate away from IIS 4.0 to supported, modern web server platforms to eliminate exposure to this and other legacy vulnerabilities. 7) Conduct regular vulnerability assessments and penetration tests focusing on legacy systems to detect similar risks.