CVE-1999-1375 is a medium-severity vulnerability affecting Microsoft Internet Information Server (IIS) versions 3.0 and 4.0. The vulnerability arises from the use of the FileSystemObject (FSO) component within an Active Server Page (ASP) script named showfile.asp. This script improperly handles user input by allowing remote attackers to specify arbitrary file names via the 'file' parameter. Because of insufficient input validation or sanitization, attackers can exploit this flaw to read arbitrary files on the server's filesystem. The vulnerability does not require authentication or user interaction, and it can be exploited remotely over the network. The impact is limited to confidentiality, as attackers can access sensitive files but cannot modify them or disrupt service availability. No patches are available for this vulnerability, and there are no known exploits in the wild documented. The CVSS score of 5.0 reflects the moderate risk posed by this vulnerability, primarily due to its ability to disclose sensitive information without requiring authentication and its relatively low complexity of exploitation.

For European organizations, this vulnerability poses a risk to the confidentiality of sensitive data hosted on IIS 3.0 and 4.0 servers running vulnerable ASP scripts. Although these IIS versions are legacy and largely obsolete, some legacy systems in critical infrastructure, government, or industrial environments might still be operational. Unauthorized disclosure of configuration files, credentials, or proprietary data could lead to further targeted attacks or compliance violations under regulations such as GDPR. The risk is heightened in sectors where legacy systems are maintained due to operational constraints, such as manufacturing, utilities, or public administration. However, the overall impact is limited by the rarity of these IIS versions in modern deployments and the absence of known active exploitation campaigns.

Given the absence of official patches, European organizations should prioritize the following mitigations: 1) Immediate identification and isolation of any IIS 3.0 or 4.0 servers still in operation, especially those exposing ASP scripts like showfile.asp. 2) Disable or remove the vulnerable showfile.asp script or any similar scripts that utilize FileSystemObject without proper input validation. 3) Implement strict input validation and sanitization on all ASP scripts to prevent arbitrary file access. 4) Restrict access to legacy IIS servers via network segmentation and firewall rules to limit exposure to untrusted networks. 5) Where possible, upgrade legacy IIS servers to supported versions with security patches and enhanced security features. 6) Conduct regular security audits and vulnerability assessments focusing on legacy systems. 7) Monitor logs for suspicious access patterns targeting file parameters in ASP pages. These steps go beyond generic advice by focusing on legacy system management, script hardening, and network-level protections tailored to this vulnerability.