CVE-1999-1473 in Internet Explorer
Summary
by MITRE
When a Web site redirects the browser to another site, Internet Explorer 3.02 and 4.0 automatically resends authentication information to the second site, aka the "Page Redirect Issue."
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Analysis
by VulDB Data Team • 04/20/2026
The CVE-1999-1473 vulnerability represents a critical security flaw in Microsoft Internet Explorer versions 3.02 and 4.0 that fundamentally compromised user authentication integrity during web navigation. This issue falls under the CWE-384 category of Session Management Flaws, specifically addressing the improper handling of authentication credentials during HTTP redirects. The vulnerability exploited a fundamental weakness in how these early browser versions managed authentication tokens when users encountered redirect scenarios, creating a significant attack surface for malicious actors.
The technical implementation of this flaw occurred when Internet Explorer encountered HTTP redirects from one web server to another. During such redirect operations, the browser automatically included previously authenticated credentials from the initial site when establishing connections to the new destination. This behavior was particularly dangerous because it occurred without user consent or awareness, effectively allowing attackers to harvest authentication information simply by crafting malicious redirect chains. The vulnerability was rooted in the browser's failure to properly isolate authentication contexts between different domains or even different paths on the same domain, violating core principles of secure web application design.
The operational impact of this vulnerability was severe and far-reaching across enterprise and individual user environments. Attackers could exploit this weakness by creating malicious web pages that would redirect users to attacker-controlled servers while automatically forwarding their authentication credentials. This created numerous attack vectors including credential theft, session hijacking, and unauthorized access to protected resources. The vulnerability was particularly concerning because it affected the most widely used web browser of its time, potentially compromising millions of users. Security researchers noted that the issue was especially dangerous in corporate environments where users might be authenticated to internal networks and then redirected to external sites, inadvertently exposing sensitive corporate credentials.
Organizations and security professionals had to implement immediate mitigations including browser configuration changes, network-level restrictions on redirect handling, and user education about avoiding suspicious links. The vulnerability highlighted the importance of proper authentication handling in web applications and led to improved security practices in subsequent browser development cycles. This issue contributed significantly to the evolution of modern web security standards and influenced the development of more robust authentication mechanisms. The problem also demonstrated the critical need for secure redirect handling in web applications and influenced the establishment of best practices for session management in web development. The vulnerability remains historically significant as one of the early examples of how browser-level security flaws could create widespread impact across the internet ecosystem.