Microsoft Outlook 98 and 2000, and Outlook Express 4.0x and 5.0x, allow remote attackers to read files on the client's system via a malformed HTML message that stores files outside of the cache, aka the "Cache Bypass" vulnerability.
https://exchange.xforce.ibmcloud.com/vulnerabilities/5013
https://docs.microsoft.com/en-us/security-updates/securitybulletins/2000/ms00-046