CVE-1999-0739 is a vulnerability affecting Microsoft Internet Information Server (IIS) version 4.0 and Microsoft Site Server. The issue arises from the presence of the codebrws.asp sample file, which allows remote attackers to read arbitrary files on the affected server. This vulnerability does not require authentication or user interaction, and it can be exploited remotely over the network. The core problem is that the codebrws.asp script improperly handles file path inputs, enabling attackers to traverse directories and access sensitive files outside the intended directory scope. This can lead to unauthorized disclosure of confidential information such as configuration files, source code, or other sensitive data stored on the server. The vulnerability has a CVSS score of 5.0, indicating a medium severity level, with an attack vector of network (AV:N), low attack complexity (AC:L), no authentication required (Au:N), and impacts confidentiality (C:P) but not integrity or availability (I:N/A:N). Microsoft has released patches to address this vulnerability, as documented in security bulletin MS99-013. There are no known exploits in the wild currently, but the vulnerability remains a concern for legacy systems still running IIS 4.0 or Site Server with the vulnerable sample file present.

For European organizations, this vulnerability poses a risk primarily to those still operating legacy IIS 4.0 servers or Microsoft Site Server installations that include the codebrws.asp sample file. Exploitation could lead to unauthorized disclosure of sensitive information, potentially exposing internal configurations, credentials, or proprietary data. This could facilitate further attacks such as privilege escalation or lateral movement within the network. Although IIS 4.0 is an outdated product, some organizations in Europe, especially in sectors with legacy infrastructure like government, manufacturing, or small enterprises, might still be vulnerable. The impact on confidentiality is significant, but there is no direct impact on system integrity or availability. The lack of known exploits reduces immediate risk, but the ease of exploitation and network accessibility mean that unpatched systems remain vulnerable to opportunistic attackers or targeted reconnaissance. Compliance with European data protection regulations (e.g., GDPR) could be jeopardized if sensitive personal data is exposed due to this vulnerability.

European organizations should prioritize identifying any IIS 4.0 or Site Server installations that include the codebrws.asp sample file. Specific mitigation steps include: 1) Applying the official Microsoft patch MS99-013 to remove or secure the vulnerable sample file and fix the underlying vulnerability. 2) If patching is not immediately possible, remove or restrict access to the codebrws.asp file by deleting it or configuring IIS to deny access to it. 3) Implement strict network segmentation and firewall rules to limit external access to legacy IIS servers. 4) Conduct thorough audits of legacy systems to identify and remediate other outdated or vulnerable components. 5) Monitor web server logs for suspicious requests attempting to access codebrws.asp or unusual file paths indicative of directory traversal attempts. 6) Plan and execute migration away from unsupported IIS versions to supported, secure platforms to eliminate exposure to legacy vulnerabilities. These steps go beyond generic advice by focusing on legacy system identification, targeted patching, and access control specific to the vulnerable sample file.