CVE-2000-0746 in IIS
Summary
by MITRE
Vulnerabilities in IIS 4.0 and 5.0 do not properly protect against cross-site scripting (CSS) attacks. They allow a malicious web site operator to embed scripts in a link to a trusted site, which are returned without quoting in an error message back to the client. The client then executes those scripts in the same context as the trusted site, aka the "IIS Cross-Site Scripting" vulnerabilities.
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Analysis
by VulDB Data Team • 05/09/2019
The vulnerability identified as CVE-2000-0746 represents a critical cross-site scripting flaw affecting Microsoft Internet Information Services versions 4.0 and 5.0. This vulnerability operates within the fundamental security model of web servers and client-side scripting environments, creating a pathway for malicious actors to exploit trust relationships between users and web applications. The flaw specifically targets the manner in which IIS handles error messages and script execution contexts, allowing attackers to manipulate the server's response handling to execute malicious code within the trusted site's security boundaries.
The technical implementation of this vulnerability stems from improper input validation and output encoding within the IIS server response mechanism. When a malicious user crafts a specially formatted link containing embedded scripts and directs traffic to a vulnerable IIS server, the server processes the request and subsequently generates error messages that contain the unescaped script content. These error messages are then returned to the client browser, where the embedded scripts execute with the privileges and security context of the trusted site. This behavior violates fundamental web security principles and creates a persistent threat vector that can compromise user sessions and data integrity. The vulnerability operates under CWE-79 which specifically addresses Cross-Site Scripting flaws in software applications.
The operational impact of this vulnerability extends far beyond simple script execution, as it enables sophisticated attack patterns that can compromise user accounts and sensitive data. Attackers can leverage this vulnerability to steal session cookies, redirect users to malicious sites, or perform actions on behalf of authenticated users. The attack vector specifically exploits the trust relationship between the client browser and the IIS server, allowing malicious code to run in the context of the legitimate website rather than appearing as an external threat. This characteristic makes detection particularly challenging for security monitoring systems and end-users, as the malicious activity appears to originate from a trusted source. The vulnerability aligns with ATT&CK technique T1059.007 which describes script-based execution methods commonly used in web-based attacks.
Mitigation strategies for CVE-2000-0746 require immediate implementation of proper input validation and output encoding mechanisms within the IIS server configuration. Organizations should implement comprehensive web application firewall rules that filter and sanitize all user input before processing, particularly focusing on URL parameters and form data that might contain script content. The recommended approach includes enabling proper HTML encoding for all dynamic content, implementing strict content security policies, and configuring IIS to sanitize error messages before transmission to clients. Additionally, network-level protections such as intrusion detection systems should be deployed to monitor for suspicious URL patterns and malformed requests that might indicate exploitation attempts. Regular security updates and patches from Microsoft should be applied immediately, as this vulnerability was addressed in subsequent security releases. The implementation of these mitigations should follow security best practices established by organizations such as the Open Web Application Security Project and the Center for Internet Security to ensure comprehensive protection against similar vulnerabilities in the future.