CVE-2003-0519 in Internet Explorer
Summary
by MITRE
Certain versions of Internet Explorer 5 and 6, in certain Windows environments, allow remote attackers to cause a denial of service (freeze) via a URL to C:\aux (MS-DOS device name) and possibly other devices.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 05/07/2019
The vulnerability described in CVE-2003-0519 represents a classic denial of service flaw affecting Internet Explorer versions 5 and 6 running on specific Windows operating systems. This weakness stems from how the browser handles URLs containing MS-DOS device names, particularly the C:ux construct, which creates a path traversal condition that can be exploited to disrupt normal browser operation. The vulnerability specifically targets the way Internet Explorer processes device names in file paths, creating an opportunity for remote attackers to manipulate the browser's handling of these special device references.
The technical implementation of this flaw involves the browser's interpretation of device names within URL structures, where C:ux represents a malformed path reference that causes the application to freeze or become unresponsive. This occurs because the browser attempts to resolve the device name reference in a manner that leads to resource exhaustion or infinite loop conditions within the application's file handling mechanisms. The vulnerability leverages the Windows file system's treatment of device names as special paths that can be accessed through normal file operations, but Internet Explorer fails to properly validate or handle these references in the context of web URLs.
The operational impact of this vulnerability extends beyond simple browser disruption to encompass broader system stability concerns. When exploited, the denial of service condition can cause Internet Explorer to freeze completely, requiring manual intervention to restore normal operation. This presents significant challenges for users who rely on web browsing for critical tasks, particularly in enterprise environments where browser availability is essential. The vulnerability affects systems where Internet Explorer 5 and 6 are installed alongside specific Windows configurations, making it relevant to organizations maintaining legacy systems or those that have not fully migrated from older browser versions.
From a cybersecurity perspective, this vulnerability aligns with CWE-129, which addresses improper validation of input, and demonstrates how device name handling can create security issues in application processing. The attack vector represents a form of resource exhaustion that falls under the broader category of denial of service attacks, potentially enabling more sophisticated exploitation techniques when combined with other vulnerabilities. Organizations should consider this weakness as part of their overall vulnerability management strategy, particularly in environments where legacy browser support is required.
Mitigation strategies for CVE-2003-0519 primarily focus on browser updates and system configuration changes. The most effective approach involves upgrading to newer versions of Internet Explorer that properly handle device names in URL contexts, though this requires careful consideration of compatibility requirements in legacy environments. System administrators should also implement URL filtering mechanisms that can block or sanitize device name references in web content, particularly when users are accessing potentially untrusted websites. Additionally, network-level protections such as proxy server configurations can help prevent exploitation by filtering out malicious URLs before they reach vulnerable browsers. The vulnerability serves as a reminder of the importance of proper input validation and the need for comprehensive security testing of applications that handle file system references in network contexts.