CVE-1999-1087: Microsoft Internet Explorer

High severity, CVSS 7.5. EPSS: 6.4% chance of exploitation in the next 30 days.

Internet Explorer 4 treats a 32-bit number ("dotless IP address") in the a URL as the hostname instead of an IP address, which causes IE to apply Local Intranet Zone settings to the resulting web page, allowing remote malicious web servers to conduct unauthorized activities by using URLs that contain the dotless IP address for their server.

Affected products

• Microsoft Internet Explorer: version 4.0 only; version 4.0.1 only

Published 1999-12-31. Last modified 2026-06-16.