CVE-1999-1164: Microsoft Outlook client allows remote attackers to cause a denial of service by sending multiple email mes...

Security readout for executives and security teams

This is an old Microsoft Outlook denial-of-service issue. A remote sender could make Outlook hang by sending multiple email messages with the same X-UIDL header. The supplied sources do not identify exact affected versions, business impact beyond client disruption, or an official fix. Exposure is most plausible where legacy Microsoft Outlook clients matching the 1999-era report remain in use. The supplied CVE data lists affected vendor and product as n/a, so precise exposure cannot be confirmed from these sources alone. Low operational priority unless legacy Outlook clients are still used. The likely impact is user disruption, not system compromise, and source evidence does not show active exploitation or affected versions. Mitigation focus: Check Microsoft guidance for affected Outlook versions and any historical fixes.; Retire or upgrade unsupported legacy Outlook clients where possible.; Monitor mail client support tickets for repeated Outlook hangs..

Prepared

Jul 1, 2026, 09:01 UTC (UTC+00:00)

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.