CVE-2003-0113 in Internet Explorer
Summary
by MITRE
Buffer overflow in URLMON.DLL in Microsoft Internet Explorer 5.01, 5.5 and 6.0 allows remote attackers to execute arbitrary code via an HTTP response containing long values in (1) Content-type and (2) Content-encoding fields.
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Analysis
by VulDB Data Team • 03/14/2025
The vulnerability identified as CVE-2003-0113 represents a critical buffer overflow flaw within the URLMON.DLL component of Microsoft Internet Explorer versions 5.01, 5.5, and 6.0. This security weakness resides in the manner these browsers handle HTTP response headers, specifically when processing the Content-Type and Content-Encoding fields. The flaw stems from insufficient input validation and bounds checking mechanisms within the URLMON.DLL library, which is responsible for handling uniform resource locators and managing web content retrieval operations. When Internet Explorer encounters HTTP responses containing excessively long values in these header fields, the application fails to properly validate the input length before copying data into fixed-size buffers, creating exploitable conditions that can lead to arbitrary code execution.
The technical implementation of this vulnerability demonstrates a classic buffer overflow condition where malicious actors can craft HTTP responses with deliberately oversized Content-Type and Content-Encoding header values. The URLMON.DLL module processes these headers without adequate boundary checks, allowing attackers to overwrite adjacent memory locations in the application's address space. This memory corruption can be manipulated to redirect program execution flow, potentially allowing remote attackers to inject and execute malicious code with the privileges of the compromised user. The vulnerability operates at the application layer and leverages the trust relationship between the browser and web servers, making it particularly dangerous as it can be exploited through standard web browsing activities without requiring any special user interaction beyond visiting a malicious website.
The operational impact of CVE-2003-0113 extends beyond simple remote code execution, as it represents a significant threat to web browser security and user system integrity. Attackers can leverage this vulnerability to gain unauthorized access to affected systems, potentially leading to complete system compromise and persistent backdoor access. The affected versions of Internet Explorer were widely deployed across corporate and personal environments, amplifying the potential attack surface and making this vulnerability particularly attractive to threat actors. This flaw directly violates security principles established in the Common Weakness Enumeration framework, specifically mapping to CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read vulnerabilities. The vulnerability also aligns with tactics described in the MITRE ATT&CK framework under the T1059.007 technique for command and scripting interpreter, as successful exploitation would enable attackers to execute arbitrary commands on compromised systems.
Mitigation strategies for this vulnerability require immediate patch deployment through Microsoft's security updates, as the original affected versions of Internet Explorer no longer receive security support. Organizations should implement network-based protections such as web application firewalls and content filtering solutions to detect and block malicious HTTP responses containing oversized headers. Browser hardening measures including disabling automatic content type detection and implementing strict header validation policies can provide additional defense layers. System administrators should consider implementing network segmentation and access controls to limit the potential impact of successful exploitation attempts. The vulnerability also underscores the importance of regular security updates and patch management programs, as it demonstrates how legacy browser versions can remain exposed to critical threats for extended periods. Security professionals should also consider implementing behavioral monitoring solutions to detect anomalous network traffic patterns that might indicate exploitation attempts targeting this specific vulnerability.