CVE-2001-0727 in Internet Explorer
Summary
by MITRE
Internet Explorer 6.0 allows remote attackers to execute arbitrary code by modifying the Content-Disposition and Content-Type header fields in a way that causes Internet Explorer to believe that the file is safe to open without prompting the user, aka the "File Execution Vulnerability."
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Analysis
by VulDB Data Team • 12/30/2024
The vulnerability described in CVE-2001-0727 represents a critical security flaw in Microsoft Internet Explorer 6.0 that exploited the browser's handling of HTTP response headers to bypass user safety prompts. This vulnerability specifically targeted the interaction between the Content-Disposition and Content-Type header fields, which are standard HTTP headers used by web servers to communicate file attributes to browsers. The flaw allowed attackers to manipulate these headers in a manner that deceived Internet Explorer into treating potentially malicious files as safe for automatic execution without user confirmation. This type of vulnerability falls under the category of content spoofing and trust relationship manipulation, where the attacker exploits the browser's trust model to execute unauthorized code.
The technical implementation of this vulnerability relied on the browser's insufficient validation of HTTP headers, particularly how it interpreted the combination of Content-Disposition and Content-Type values. When Internet Explorer received a web response with carefully crafted headers, it would incorrectly determine that the file was safe to execute automatically, even if it contained malicious code such as ActiveX controls or other executable content. This flaw was particularly dangerous because it bypassed the browser's built-in security mechanisms that typically prompt users before executing potentially harmful content. The vulnerability exploited a weakness in the browser's security model where the Content-Disposition header, which normally controls how files should be handled, could be manipulated to override the Content-Type header's security implications.
From an operational perspective, this vulnerability created a significant attack surface that allowed remote code execution without user interaction, making it extremely dangerous in enterprise environments. Attackers could craft malicious web pages or web services that would automatically execute harmful code on vulnerable systems when users visited the malicious sites. The impact extended beyond individual user systems to potentially compromise entire networks, as the vulnerability could be exploited through various attack vectors including phishing emails, compromised websites, or malicious web applications. This vulnerability contributed to the broader landscape of browser-based attacks that were prevalent during the early 2000s, demonstrating how seemingly minor header parsing issues could lead to complete system compromise.
The exploitation of this vulnerability aligns with several ATT&CK techniques including T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter), as it enabled attackers to execute arbitrary code on target systems. From a CWE perspective, this vulnerability maps to CWE-170, which deals with improper handling of input that can lead to security issues, and potentially CWE-20, which addresses improper input validation. The vulnerability also reflects broader security principles related to defense in depth, where the lack of proper header validation created a single point of failure that attackers could exploit. Organizations affected by this vulnerability needed to implement immediate mitigations including browser updates, network-level filtering, and user education about the dangers of visiting untrusted websites. The incident highlighted the importance of proper HTTP header validation and the need for robust security models in web browsers, contributing to improved security practices in subsequent browser development cycles and establishing the foundation for more sophisticated security measures in modern web browsers.