CVE-1999-1164: Microsoft Outlook

Medium severity, CVSS 5.0. EPSS: 13.2% chance of exploitation in the next 30 days.

Microsoft Outlook client allows remote attackers to cause a denial of service by sending multiple email messages with the same X-UIDL headers, which causes Outlook to hang.

Affected products

• Microsoft Outlook: version 97 only; version 98 only; version 2000 only
• Microsoft Outlook Express: any version

Published 1999-06-25. Last modified 2026-06-16.