CVE-1999-0891 in Internet Explorer
Summary
by MITRE
The "download behavior" in Internet Explorer 5 allows remote attackers to read arbitrary files via a server-side redirect.
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Analysis
by VulDB Data Team • 02/23/2025
The vulnerability described in CVE-1999-0891 represents a significant security flaw in Internet Explorer 5's handling of server-side redirects during file downloads. This issue stems from the browser's improper validation of redirect responses that occur during the download process, creating an avenue for malicious actors to exploit the client-side behavior and gain unauthorized access to files on the target system. The vulnerability specifically targets the download behavior mechanism that Internet Explorer employs when processing HTTP redirects, allowing attackers to manipulate the browser's download process through crafted server responses. This flaw operates at the intersection of web browser security and server-side response handling, where the client's trust in redirect responses creates an exploitable gap in the security model.
The technical implementation of this vulnerability relies on the browser's failure to properly validate the destination of redirected downloads. When Internet Explorer encounters a server-side redirect during a download operation, it follows the redirect without sufficient verification of the target location. Attackers can leverage this by setting up malicious servers that respond to download requests with redirects to local file system paths or network shares. The browser's download mechanism, designed to handle legitimate redirects from web servers to other web servers, fails to distinguish between safe and malicious redirect targets, enabling attackers to traverse the file system and potentially access sensitive data. This behavior aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as path traversal vulnerabilities. The vulnerability essentially allows attackers to bypass normal file access controls by exploiting the browser's trust in redirect responses.
The operational impact of CVE-1999-0891 extends beyond simple information disclosure, as it provides attackers with the capability to access arbitrary files on the target system. This includes potentially sensitive configuration files, user data, system files, and other resources that should normally be protected from unauthorized access. The vulnerability is particularly dangerous because it can be exploited through web-based attacks without requiring any special privileges or local access to the target system. Attackers can craft malicious web pages or redirect URLs that, when clicked, trigger the vulnerable download behavior and silently transfer files to their own systems. This vulnerability significantly weakens the security boundaries that browsers typically establish between the user's system and web content, creating a persistent threat vector that can be exploited across different network environments. The impact is further amplified by the widespread use of Internet Explorer 5 during the late 1990s, making this vulnerability particularly dangerous in enterprise and consumer environments.
Mitigation strategies for this vulnerability require a multi-layered approach that addresses both the immediate security gap and broader browser security practices. Users should implement strict browser security settings that limit the ability of web pages to initiate downloads from untrusted sources, while administrators should configure network firewalls to restrict access to sensitive file systems and network shares. The most effective long-term solution involves updating to newer browser versions that properly validate redirect responses and implement stronger security boundaries during download operations. Organizations should also deploy web application firewalls and content filtering solutions that can detect and block malicious redirect patterns. This vulnerability demonstrates the importance of proper input validation and the principle of least privilege in web browser security, as highlighted in various ATT&CK framework techniques related to privilege escalation and information gathering. The security community should emphasize the need for comprehensive browser security testing that includes edge cases involving redirect behaviors and server-side interactions. Additionally, implementing proper network segmentation and access controls can help limit the potential damage from such vulnerabilities by restricting access to sensitive resources even if an attacker successfully exploits the download behavior flaw.