CVE-1999-0739 in IIS
Summary
by MITRE
The codebrws.asp sample file in IIS and Site Server allows remote attackers to read arbitrary files.
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Analysis
by VulDB Data Team • 10/23/2025
The vulnerability identified as CVE-1999-0739 represents a critical directory traversal flaw in Microsoft Internet Information Services and Microsoft Site Server products. This security weakness exists within the codebrws.asp sample file, which was designed to provide developers with a basic browsing interface for code samples. The flaw enables remote attackers to exploit improper input validation mechanisms, allowing them to access files beyond the intended scope of the web application. The vulnerability stems from insufficient sanitization of user-supplied input parameters that are directly used in file system operations without proper authorization checks or path validation.
This directory traversal vulnerability operates at the application layer and specifically targets the web server's file access mechanisms. Attackers can manipulate input parameters to navigate through the file system hierarchy and retrieve sensitive files that should normally be restricted. The flaw is particularly dangerous because it allows arbitrary file reading capabilities, potentially exposing configuration files, source code, database credentials, and other sensitive information. The vulnerability affects systems running IIS versions prior to 5.0 and Site Server versions that included the vulnerable codebrws.asp sample file. This issue demonstrates a classic lack of input validation and proper access controls, which aligns with CWE-22 - Improper Limitation of a Pathname to a Restricted Directory.
The operational impact of this vulnerability extends beyond simple information disclosure. Remote attackers can leverage this flaw to gain insights into the system architecture, potentially identifying other vulnerabilities through access to configuration files and source code. The vulnerability enables attackers to read system files that may contain sensitive data such as database connection strings, application passwords, or other credentials stored in plain text. Additionally, the ability to access arbitrary files could lead to more severe consequences including privilege escalation opportunities or the discovery of other system vulnerabilities that could be exploited for further compromise. This vulnerability affects both the web server's security posture and the overall confidentiality of the information systems it protects.
Mitigation strategies for CVE-1999-0739 involve immediate patching of affected systems with the appropriate Microsoft security updates. Organizations should ensure that all IIS and Site Server installations are updated to versions that address this directory traversal vulnerability. Network segmentation and proper access controls should be implemented to limit exposure of vulnerable applications. Input validation mechanisms should be strengthened to prevent improper path traversal attempts, and the principle of least privilege should be enforced when configuring web server permissions. Regular security assessments and vulnerability scanning should be conducted to identify similar issues in other applications. The remediation efforts should align with the ATT&CK framework's T1213 - Data from Information Repositories tactic, emphasizing the importance of protecting information repositories from unauthorized access. System administrators should also consider implementing web application firewalls and additional monitoring to detect suspicious file access patterns that could indicate exploitation attempts.