CVE-1999-1591: Microsoft Internet Information Server

High severity, CVSS 7.5. EPSS: 11.3% chance of exploitation in the next 30 days.

Microsoft Internet Information Services (IIS) server 4.0 SP4, without certain hotfixes released for SP4, does not require authentication credentials under certain conditions, which allows remote attackers to bypass authentication requirements, as demonstrated by connecting via Microsoft Visual InterDev 6.0.

Affected products

• Microsoft Internet Information Server: version 4.0 only
• Microsoft Visual Interdev: version 6.0 only

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