CVE-2003-1484 in Internet Explorer
Summary
by MITRE
Microsoft Internet Explorer 6.0 SP1 allows remote attackers to cause a denial of service (crash) by creating a DHTML link that uses the AnchorClick "A" object with a blank href attribute.
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Analysis
by VulDB Data Team • 05/07/2019
Microsoft Internet Explorer 6.0 Service Pack 1 contains a critical denial of service vulnerability that stems from improper handling of DHTML link objects within the browser's rendering engine. This vulnerability specifically manifests when the browser encounters a DHTML anchor element configured with the AnchorClick "A" object and a blank href attribute, creating a condition that leads to application instability and potential system crashes. The flaw resides in the browser's inability to properly validate and process malformed hyperlink references during dynamic HTML content rendering, particularly when the href attribute is intentionally left empty or contains only whitespace characters.
The technical implementation of this vulnerability leverages the browser's DHTML object model where the AnchorClick "A" object is designed to handle click events on anchor elements. When an attacker crafts a malicious HTML page containing an anchor element with the AnchorClick object and a blank href attribute, the browser's JavaScript engine fails to properly handle the empty reference, resulting in memory corruption or stack overflow conditions. This processing error occurs within the browser's HTML parser and DOM manipulation components, specifically affecting the way IE handles dynamic anchor element events. The vulnerability is classified under CWE-121 as a stack-based buffer overflow condition, though it manifests more accurately as a heap-based memory corruption issue during dynamic object instantiation.
The operational impact of this vulnerability extends beyond simple browser instability, as it can be exploited in various attack scenarios including web-based phishing campaigns, malicious website redirection, and cross-site scripting attempts. Attackers can leverage this flaw to disrupt user sessions, cause unexpected browser termination, or potentially create conditions that allow for more sophisticated attacks if combined with other vulnerabilities. The vulnerability affects the core browser functionality and can be triggered through simple HTML content without requiring any special privileges or user interaction beyond visiting a malicious website. This makes it particularly dangerous in enterprise environments where users may inadvertently encounter compromised content through email attachments, web browsing, or social engineering tactics.
Mitigation strategies for this vulnerability include applying the official Microsoft security patch released for Internet Explorer 6.0 SP1, which addresses the specific memory handling issue in the DHTML object model. Organizations should implement browser hardening measures such as disabling DHTML scripting capabilities where possible, using content filtering solutions, and maintaining updated security policies that restrict access to untrusted websites. Network-level protections can include implementing web proxies with content filtering capabilities that can detect and block malicious HTML content containing blank href attributes. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping browser software updated. The vulnerability demonstrates the importance of proper input validation and memory management in browser applications, aligning with ATT&CK technique T1210 for exploitation of memory corruption vulnerabilities. Organizations should also consider implementing browser sandboxing solutions and regular security assessments to identify similar issues in legacy browser environments.