CVE-2004-1639 in Mozilla
Summary
by MITRE
Mozilla Firefox before 0.10, Mozilla 5.0, and Gecko 20040913 allows remote attackers to cause a denial of service (application crash or memory consumption) via a large binary file with a .html extension.
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Analysis
by VulDB Data Team • 07/08/2017
The vulnerability described in CVE-2004-1639 represents a significant denial of service flaw affecting early versions of Mozilla Firefox and the underlying Gecko rendering engine. This issue specifically targets the browser's handling of file extensions and content parsing mechanisms, where the software fails to properly validate file types before processing them. The vulnerability manifests when users encounter or attempt to open binary files that have been renamed with the .html extension, creating a scenario where the browser's parser becomes overwhelmed during content interpretation. This flaw falls under the category of improper input validation and demonstrates how seemingly innocuous file extension manipulation can lead to system instability.
The technical implementation of this vulnerability exploits the Gecko engine's content type detection and processing logic. When Firefox encounters a file with an .html extension, it automatically assumes the file should be processed as HTML content regardless of its actual binary nature. The parser attempts to interpret binary data as structured markup language, leading to memory allocation issues and potential buffer overflows within the rendering engine. This behavior creates an exploitable condition where remote attackers can craft malicious files that, when opened or even just accessed by the browser, trigger excessive memory consumption or application crashes. The vulnerability is particularly dangerous because it operates at the content parsing layer, meaning it can be triggered through various attack vectors including web downloads, email attachments, or even malicious websites that serve such files.
The operational impact of CVE-2004-1639 extends beyond simple browser instability to potentially enable more sophisticated attacks within the broader context of browser exploitation. While the primary effect is denial of service, this vulnerability could serve as a stepping stone for attackers seeking to establish more persistent compromises. The memory consumption aspect of the vulnerability aligns with common attack patterns documented in the attack tree framework, where initial resource exhaustion can be followed by more complex exploitation techniques. This flaw particularly affects users of older browser versions where security patches were not yet available, creating a window of opportunity for adversaries to exploit the predictable behavior of the rendering engine. The vulnerability demonstrates the importance of proper content type validation and the dangers of assuming file extensions accurately represent content structure.
Mitigation strategies for this vulnerability involve multiple layers of defense that align with established security practices and industry standards. The primary recommendation is immediate patching of affected browser versions to ensure proper file type validation and content parsing. Organizations should implement content filtering mechanisms that prevent execution of binary files with HTML extensions, particularly in email and web environments. This approach corresponds to the principle of least privilege and content validation practices outlined in various cybersecurity frameworks including the NIST Cybersecurity Framework. Network administrators should consider implementing web application firewalls that can detect and block suspicious file type associations. Additionally, user education regarding suspicious file downloads and the importance of verifying file types before opening them provides an additional defensive layer. The vulnerability highlights the critical importance of maintaining up-to-date software versions and demonstrates how seemingly simple parsing flaws can have significant security implications, reinforcing the need for comprehensive security testing and validation of content handling mechanisms.