CVE-1999-0465 is a high-severity vulnerability identified in 1999 affecting the Lynx text-based web browser and Microsoft Internet Explorer. The vulnerability arises from the improper handling of the IMG HTML tag's width parameter. Specifically, remote attackers can craft a malicious web page containing an IMG tag with an excessively large width attribute value. When a vulnerable browser processes this tag, it triggers a crash, resulting in a denial of service (DoS) condition. The root cause is likely due to insufficient input validation or integer overflow/underflow issues in the rendering engine's handling of image dimensions. Since the vulnerability requires no authentication and can be exploited remotely simply by visiting a malicious web page, it poses a significant risk to users of these browsers. The CVSS score of 10.0 reflects the critical impact on confidentiality, integrity, and availability, indicating that exploitation could lead to complete compromise or disruption of the affected system. However, no patches are available for this vulnerability, and there are no known exploits in the wild documented. Given the age of this vulnerability and the obsolescence of Lynx and early versions of Internet Explorer, modern systems are unlikely to be affected unless legacy software is still in use.

For European organizations, the primary impact of CVE-1999-0465 would be service disruption due to browser crashes, potentially affecting user productivity and availability of web-based applications accessed via vulnerable browsers. Although the vulnerability does not directly lead to data theft or system compromise, the complete crash of browsers can be exploited to cause denial of service. In environments where Lynx or early Internet Explorer versions are still used—such as legacy industrial control systems, archival systems, or specialized research environments—this vulnerability could disrupt critical operations. Additionally, if attackers combine this DoS with other attack vectors, it could facilitate further exploitation. However, given the age and lack of patch availability, most modern European organizations are unlikely to be impacted unless legacy systems remain in operation without mitigation.

Since no official patches exist for CVE-1999-0465, mitigation focuses on reducing exposure and preventing exploitation. Organizations should: 1) Decommission or upgrade legacy systems running Lynx or early Internet Explorer versions to modern, supported browsers that have addressed this vulnerability. 2) Implement network-level protections such as web filtering and intrusion prevention systems (IPS) to block malicious web pages containing suspiciously large IMG width parameters or malformed HTML content. 3) Employ endpoint protection solutions that can detect abnormal browser crashes and isolate affected systems to prevent wider impact. 4) Educate users to avoid accessing untrusted or suspicious websites, especially on legacy browsers. 5) For environments where legacy browsers must be used, consider sandboxing or running them in isolated virtual machines to contain potential crashes and prevent disruption to critical systems.