XADM: AUTHINFO Command Causes Information Store Problems

A malicious attacker could connect to the NNTP port of an Exchange Server 5.5 or 5.0 machine and disrupt the information store process by issuing specific sequences of AUTHINFO commands.

When this occurs, an application error similar to one of the following may occur:

• The instruction at "0x00611a00" referenced memory at "0x8b4475db". The memory could not be "read".
  The instruction at "0x005cd600" referenced memory at "0x068fb87a". The memory could not be "written".

In addition, the Exchange Server information store may stop unexpectedly, causing the Internet Mail Service and other Exchange Server information services to no longer function properly.

Improper checking of bounds conditions on certain AUTHINFO command sequences can result in a buffer overflow.

Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.0.

A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next service pack that contains this fix. Contact Microsoft Technical Support for more information.

This fix has been posted to the following Internet location:


Microsoft has confirmed this to be a problem in Microsoft Exchange Server version 5.5. This problem has been corrected in the latest U.S. service pack for Microsoft Exchange Server version 5.5. For information on obtaining the service pack, query on the following word in the Microsoft Knowledge Base (without the spaces):