CVE-1999-0465 in Internet Explorer
Summary
by MITRE
Remote attackers can crash Lynx and Internet Explorer using an IMG tag with a large width parameter.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-1999-0465 represents a classic buffer overflow condition affecting web browsers through improper handling of HTML image tags. This issue specifically targets the Lynx text-based browser and Microsoft Internet Explorer web browser implementations, demonstrating how seemingly benign HTML elements can be weaponized to cause system instability. The flaw manifests when browsers encounter an img tag containing an exceptionally large width parameter value, triggering memory corruption that results in application crashes and potential system instability.
The technical implementation of this vulnerability stems from inadequate input validation within browser rendering engines. When processing HTML content, both Lynx and Internet Explorer failed to properly sanitize or limit the width attribute values in img tags, allowing attackers to specify arbitrary large numerical values. This lack of bounds checking creates a condition where the browser's memory allocation routines receive oversized parameters that exceed the intended buffer limits. The vulnerability operates at the application layer and can be exploited through web content delivery, making it particularly dangerous in web browsing environments where users may encounter maliciously crafted HTML pages.
The operational impact of this vulnerability extends beyond simple browser crashes to potentially enable more sophisticated attack vectors. While the immediate effect is system instability and application termination, the underlying buffer overflow condition could theoretically be exploited to execute arbitrary code if proper memory protection mechanisms are not in place. The vulnerability affects a broad user base since both Lynx and Internet Explorer were widely deployed browsers at the time of discovery, with Lynx being particularly popular among users requiring text-based browsing and Internet Explorer dominating the desktop browser market. This widespread adoption meant that successful exploitation could affect numerous users across different computing environments.
Security professionals should recognize this vulnerability as a precursor to more sophisticated buffer overflow attacks that would later be categorized under CWE-121, which specifically addresses stack-based buffer overflow conditions. The attack pattern aligns with techniques described in the ATT&CK framework under the T1203 category for legitimate program execution, where malicious code is executed through web browser vulnerabilities. Mitigation strategies should include implementing proper input validation and bounds checking within browser rendering engines, applying security patches promptly, and configuring browsers to limit HTML attribute values to reasonable ranges. Organizations should also consider implementing web application firewalls and content filtering solutions to prevent delivery of malicious HTML content that could exploit this vulnerability.
The remediation approach for this vulnerability requires browser vendors to implement comprehensive input validation mechanisms that prevent oversized parameter values from being processed by the rendering engines. This includes establishing maximum limits for HTML attribute values and implementing proper memory management practices to prevent buffer overflows. Additionally, users should be educated about the risks of visiting untrusted websites and the importance of keeping browser software updated with the latest security patches. The vulnerability serves as an important example of how fundamental security principles like input validation and bounds checking must be implemented throughout software development processes to prevent exploitation through seemingly simple attack vectors that can cause significant operational disruption.