CVE-2004-0203 in Exchange
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in Outlook Web Access for Exchange Server 5.5 Service Pack 4 allows remote attackers to insert arbitrary script and spoof content in HTML email or web caches via an HTML redirect query.
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Analysis
by VulDB Data Team • 07/13/2025
The vulnerability identified as CVE-2004-0203 represents a critical cross-site scripting flaw within Microsoft Outlook Web Access component of Exchange Server 5.5 Service Pack 4. This security weakness resides in the web-based email interface that allows users to access their email accounts through a web browser. The vulnerability specifically manifests when the system processes HTML redirect queries without proper input sanitization, creating an avenue for malicious actors to inject arbitrary script code into the web application's response. The flaw stems from inadequate validation of user-supplied input within the web interface, particularly in how the system handles HTML redirect parameters that are commonly used for navigation within web applications.
The technical implementation of this vulnerability aligns with CWE-79, which categorizes cross-site scripting as a code injection flaw where untrusted data is embedded into web pages viewed by other users. The attack vector exploits the web application's failure to properly escape or filter HTML characters within redirect query parameters, allowing attackers to inject malicious scripts that execute in the context of other users' browsers. When a victim accesses a maliciously crafted URL containing the injected script, the code executes within their browser session, potentially compromising their email communications and personal data. This vulnerability operates at the application layer and specifically targets the user interface components that handle HTML rendering and navigation within the web-based email environment.
The operational impact of CVE-2004-0203 extends beyond simple script injection, as it enables sophisticated attacks that can lead to complete session hijacking and data exfiltration. Attackers can craft malicious links that redirect users to phishing pages designed to steal authentication credentials or manipulate email content, effectively allowing unauthorized access to sensitive corporate communications. The vulnerability also enables content spoofing where attackers can modify the appearance of legitimate emails, potentially deceiving users into believing they are viewing authentic messages from trusted sources. Additionally, since the vulnerability affects web caches, malicious scripts can persist and affect multiple users who access cached versions of compromised pages, amplifying the attack scope. The attack can be executed remotely without requiring any special privileges or access to the underlying Exchange server infrastructure.
Mitigation strategies for this vulnerability should encompass multiple defensive layers to address both immediate exposure and prevent future similar issues. Organizations should implement comprehensive input validation and output encoding mechanisms within the web application to sanitize all user-supplied data before processing or rendering. The most effective immediate solution involves applying Microsoft security patches and updates for Exchange Server 5.5 Service Pack 4, which would include the necessary code modifications to properly escape HTML characters in redirect queries. Network-level protections such as web application firewalls and content filtering systems can provide additional defense-in-depth by monitoring for suspicious script injection patterns in HTTP requests. Security monitoring should include regular scanning for XSS vulnerabilities using automated tools and manual code reviews focused on input handling routines. The implementation of proper HTTP headers including Content Security Policy directives can further restrict script execution and reduce the impact of successful XSS attacks, while regular security awareness training for users helps prevent social engineering aspects of such attacks. Organizations should also consider implementing a comprehensive web security posture management program that includes regular vulnerability assessments and penetration testing to identify similar weaknesses in other web applications.