Title: Microsoft Exchange Server 2003 Outlook Web Access Random Mailbox Access Vulnerability
Severity: HIGH
Description:
Microsoft Exchange Server 2003 is an e-mail and directory server offered by Microsoft. Outlook Web Access (OWA) is a service provided by Exchange server that allows users to access their Exchange mailbox via the web.
A vulnerability exists that could allow an authenticated OWA user to connect to another OWA user's mailbox. Only mailboxes recently accessed through OWA on the same Exchange server could be accessed in this way. An attacker could not choose which mailbox to connect to; the connection would be random.
The vulnerability only exists when the back-end Exchange server hosting the OWA mailboxes is configured not to use Kerberos authentication with the front-end Exchange server running on the IIS server. In this case, authentication would fall back to NTLM authentication. The only method for exposing the vulnerability in this way without intervention by an administrator would be through the weakness described in BID 9118.
When these circumstances occur, the front-end Exchange server will periodically attempt to authenticate with the back-end server using Kerberos authentication. On these requests, IIS 6 will ignore the Kerberos authentication and allow access to the open connections that were already authenticated with NTLM.
Successful exploitation of this vulnerability could allow a remote attacker to access sensitive information in another user's mailbox or send email as that user.
Affected Products:
- Microsoft Exchange Server 2003
References:
- Microsoft: Microsoft Security Bulletin MS04-002
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