CVE-2001-0875 in Internet Explorer
Summary
by MITRE
Internet Explorer 5.5 and 6.0 allows remote attackers to cause the File Download dialogue box to misrepresent the name of the file in the dialogue in a way that could fool users into thinking that the file type is safe to download.
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Analysis
by VulDB Data Team • 03/29/2025
This vulnerability in Internet Explorer 5.5 and 6.0 represents a significant security flaw that exploits user trust in file download interfaces. The issue stems from improper validation of file names during the download process, allowing attackers to manipulate how file names appear in the download dialog box. This manipulation occurs when the browser fails to properly sanitize or validate the filename parameter in HTTP headers, specifically in the content-disposition header that controls how files are presented to users. The vulnerability falls under CWE-20, which addresses improper input validation, and more specifically relates to CWE-1004, concerning insecure default permissions in web applications.
The technical implementation of this attack involves crafting malicious HTTP responses where the server sends a content-disposition header with a deceptive filename that differs from the actual file being served. When users encounter the download dialog, they may see a seemingly benign filename such as "update.exe" or "readme.txt" while the actual file could be a malicious executable or script. This misrepresentation occurs because Internet Explorer does not adequately verify the filename provided in the HTTP response headers against the actual file content or perform proper sanitization of the filename string before displaying it to users.
The operational impact of this vulnerability extends beyond simple phishing attacks, as it enables sophisticated social engineering campaigns where attackers can exploit user confidence in familiar file types. Users may download files believing they are receiving legitimate updates or documents while unknowingly executing malicious code. This vulnerability is particularly dangerous because it operates at the user interface level, bypassing traditional security mechanisms that focus on content inspection rather than presentation. The attack vector aligns with ATT&CK technique T1195.001, which covers 'Phishing: Spearphishing Attachment', and T1203, 'Exploitation for Client Execution', as it enables execution of malicious code through deceptive file presentation.
Mitigation strategies for this vulnerability include implementing proper input validation on web servers to sanitize filename parameters in HTTP headers, updating to newer versions of Internet Explorer that address this flaw, and deploying user education programs to recognize potentially deceptive download prompts. Organizations should also consider implementing network-level controls such as proxy servers that can inspect and filter HTTP headers, as well as browser security policies that restrict automatic execution of downloaded files. The vulnerability demonstrates the importance of defense in depth, where multiple layers of security are necessary to protect against attacks that exploit user trust in familiar interfaces. This issue highlights the critical need for proper security testing of user-facing interfaces and the potential consequences of insufficient input validation in web applications.