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Microsoft Security Bulletin MS98-012 - Critical

Updates available for Security Vulnerabilities in Microsoft PPTP

Published: August 18, 1998 | Updated: March 10, 2003

Version: 2.0

Patch Availability Information Updated: March 10, 2003
Originally Posted: August 18, 1998
Last Revised: August 18, 1998

Summary

Microsoft has released a set of patches that fix several security issues with implementations of the Point-to-Point Tunneling Protocol (PPTP) used in Microsoft Virtual Private Networking (VPN) products. Customers using affected software listed below to secure communcations over a public network (i.e. the Internet) should download and apply these patches as soon as possible.

Customers who are not using PPTP for network security are not affected by this issue.

Issue

The Microsoft implementation of PPTP uses MS-CHAP for user authentication and Microsoft Point-to-Point Encryption (MPPE) to protect the confidentiality of user data. Potential vulnerabilities addressed by these updates include:

  • Dictionary attack against the LAN Manager authentication information
  • Password theft
  • PPTP server spoofing
  • Reuse of MPPE session keys

While there have not been any reports of customers being adversely affected by these problems, Microsoft is releasing these patches to address the implied risks posed by these issues.

Affected Software Versions

The following software is affected by this vulnerability:

  • Microsoft Dialup Networking 1.2x and earlier on Windows 95
  • Microsoft Remote Access Services on Windows NT 4.0 (both client and server)
  • Microsoft Routing and Remote Access Services on Windows NT Server 4.0
  • Microsoft Windows 98 Dialup Networking

What Microsoft is Doing

On August 18th Microsoft released a set of patches that fix the problems identified. These patches are available for download by Windows NT, Windows 95 and Windows 98 customers from the Microsoft FTP site.

Microsoft has sent this security bulletin to customers subscribing to the Microsoft Product Security Notification Service. See The Microsoft Product Security Notification Service for more information about this free customer service.

Microsoft has published the following Knowledge Base (KB) articles on this issue:

What customers should do

Microsoft highly recommends that users of affected software versions, listed in the "Affected Software Versions" section above, should download the appropriate patch. Complete URLs for each affected software version is given below.

Windows NT 4.0 RAS Users

Download the patch from:

http://www.microsoft.com/technet/security/patchavailability.mspx

Windows NT 4.0 RRAS Users

Download the patch from:

http://www.microsoft.com/technet/security/patchavailability.mspx

Windows 95 Users

Download the patch from:

http://www.microsoft.com/technet/security/patchavailability.mspx

Windows 98 Users

Download the patch from:

http://www.microsoft.com/technet/security/patchavailability.mspx

Strong Encryption Versions (128-bit)

Customers in the United States and Canada can download the strong encryption versions of these updates from:

http://www.microsoft.com/technet/security/patchavailability.mspx

More Information

Please see the following references for more information related to this issue.

Revisions

  • August 18, 1998: Bulletin Created
  • V2.0 (March 10, 2003): Introduced versioning and updated patch availability information

For additional security-related information about Microsoft products, please visit http://www.microsoft.com/technet/security

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