CVE-2003-0530 in Internet Explorer
Summary
by MITRE
Buffer overflow in the BR549.DLL ActiveX control for Internet Explorer 5.01 SP3 through 6.0 SP1 allows remote attackers to execute arbitrary code.
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Analysis
by VulDB Data Team • 12/31/2024
The vulnerability identified as CVE-2003-0530 represents a critical buffer overflow flaw within the BR549.DLL ActiveX control that affects Internet Explorer versions 5.01 Service Pack 3 through 6.0 Service Pack 1. This vulnerability exists at the core of Microsoft's web browser architecture where ActiveX controls are designed to extend browser functionality through component object model interfaces. The BR549.DLL control specifically handles telecommunications protocols and data transmission functions within the browser environment, making it a prime target for exploitation due to its widespread deployment and privileged execution context. The buffer overflow occurs when the control processes untrusted input data through various parameters, creating a condition where maliciously crafted data can overwrite adjacent memory locations beyond the allocated buffer boundaries.
The technical exploitation of this vulnerability leverages the inherent design flaw in how the BR549.DLL control manages memory allocation and input validation. When Internet Explorer loads a webpage containing malicious ActiveX code that invokes the vulnerable BR549.DLL control, the control's parameter handling routines fail to properly validate the length of input data before copying it into fixed-size memory buffers. This classic buffer overflow condition allows attackers to overwrite critical memory segments including return addresses, function pointers, and other control structures within the executing process. The vulnerability maps directly to CWE-121, which categorizes buffer overflow conditions that occur when data is copied into a buffer without proper bounds checking, and aligns with CWE-125, which addresses out-of-bounds read conditions that can lead to memory corruption. Attackers can exploit this flaw by crafting malicious web content that triggers the vulnerable control, potentially leading to arbitrary code execution with the privileges of the currently logged-in user.
The operational impact of CVE-2003-0530 extends beyond simple code execution, as it provides attackers with a powerful foothold for further exploitation within compromised systems. Since ActiveX controls run with the security context of the user who launched Internet Explorer, successful exploitation can enable attackers to perform actions such as installing malware, modifying system files, accessing sensitive data, or establishing persistent backdoors. The vulnerability's prevalence across multiple Internet Explorer versions from 5.01 SP3 through 6.0 SP1 meant that a significant portion of the web browsing population was potentially exposed to this threat, particularly in enterprise environments where older browser versions were commonly deployed. The attack vector is particularly dangerous because it requires no special privileges from the end-user, as the vulnerability can be triggered through normal web browsing activities when visiting malicious websites. This makes the exploit highly effective for drive-by download attacks and mass deployment campaigns, aligning with ATT&CK technique T1059.005 for command and scripting interpreter execution through web-based interfaces.
Mitigation strategies for CVE-2003-0530 must address both immediate remediation and long-term security posture improvements. The primary defense involves updating Internet Explorer to versions that contain patches for this vulnerability, specifically Microsoft Internet Explorer 6.0 Service Pack 2 or later, which included memory protection enhancements and improved input validation. Organizations should also implement ActiveX control restrictions through group policies that prevent the automatic execution of potentially dangerous controls or require explicit user approval before loading such components. Additional protective measures include deploying web application firewalls that can detect and block malicious ActiveX control requests, implementing strict browser security settings that disable ActiveX controls by default, and maintaining comprehensive network monitoring to detect exploitation attempts. The vulnerability serves as a critical example of why defense-in-depth strategies are essential, as relying solely on perimeter security measures proves insufficient against attacks targeting browser-based execution environments. Security professionals should also consider implementing application whitelisting policies that only allow trusted ActiveX controls to execute, thereby reducing the attack surface available to potential adversaries.