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Microsoft Security Bulletin MS00-046

Patch Available for 'Cache Bypass' Vulnerability

Originally Posted: July 20, 2000


Microsoft has released a patch that eliminates a security vulnerability in Microsoft® Outlook® and Outlook Express. The vulnerability could allow a malicious user to send an HTML mail that, when opened, could read, but not add, change or delete, files on the recipient's computer. If coupled with other vulnerabilities, it could potentially be used in more advanced attacks as well.

The patch eliminates this vulnerability as well as those discussed in Microsoft Security Bulletins MS00-043 and MS00-045. Customers who already have taken the corrective action discussed in either of these bulletins do not need to take any additional action.

Affected Software:

  • Microsoft Outlook Express 4.x
  • Microsoft Outlook Express 5.x
  • Microsoft Outlook 98
  • Microsoft Outlook 2000

Vulnerability Identifier: CVE-2000-0621

General Information

Technical details

Frequently asked questions

Patch availability

Other information:

Support: This is a fully supported patch. Information on contacting Microsoft Technical Support is available at .

Security Resources: The Microsoft TechNet Security Web Site provides additional information about security in Microsoft products.


The information provided in the Microsoft Knowledge Base is provided "as is" without warranty of any kind. Microsoft disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose. In no event shall Microsoft Corporation or its suppliers be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Microsoft Corporation or its suppliers have been advised of the possibility of such damages. Some states do not allow the exclusion or limitation of liability for consequential or incidental damages so the foregoing limitation may not apply.


  • July 20, 2000: Bulletin Created.