CVE-1999-1577: Microsoft Internet Explorer

Medium severity, CVSS 5.1. EPSS: 19.5% chance of exploitation in the next 30 days.

Buffer overflow in HHOpen ActiveX control (hhopen.ocx) 1.0.0.1 for Internet Explorer 4.01 and 5 allows remote attackers to execute arbitrary commands via long arguments to the OpenHelp method.

Affected products

• Microsoft Internet Explorer: version 4.0.1 only; version 5.0 only

Published 1999-10-31. Last modified 2026-06-16.