IIS Internal IP Address Disclosure (#NISR05032002B)

From: David Litchfield (nisr@NEXTGENSS.COM)
Date: 03/05/02 

Date:         Tue, 5 Mar 2002 17:58:24 -0000
From: David Litchfield <nisr@NEXTGENSS.COM>
To: NTBUGTRAQ@LISTSERV.NTBUGTRAQ.COM

NGSSoftware Insight Security Research Advisory

Name: Internal IP Addresses and IIS
Systems Affected: Microsoft IIS 4/5/5.1
Platforms: Windows NT/2000/XP
Severity: Low Risk
Vendor URL: http://www.microsoft.com/
Author: David Litchfield (david@nextgenss.com)
Date: 4th March 2002
Advisory number: #NISR05032002B
Advisory URL: http://www.nextgenss.com/advisories/iisip.txt

Issue: Possible to discover internal IP addresses used
                                by IIS Servers

Description
***********
Microsoft's Internet Information Server offers web, ftp, mail and nntp
services. If the server is protected by a firewall using Network Address
Translation and the server uses a private internal IP address then, by
making a malformed request to the web service it is possible for an
attacker to discover this IP address. Whilst this won't come anywhere
near to allowing an attacker to compromise a IIS server it will help
them formulate further attacks. This issue is similar to the issue
documented at
http://support.microsoft.com/default.aspx?scid=KB;EN-US;Q218180&id=KB;EN
-US;Q218180

Details
*******
By making certain requests to the web service with a blank Host HTTP
client header the server response will often contain the server's IP
address, for example when using the PROPFIND request method.

PROPFIND / HTTP/1.1
Host:
Content-Length: 0

The server will return a 207 Multi-Status response with certain
properties of the root page. The server's IP address will be revealed if
the HREF property. Using the WRITE or MKCOL method will return the
machine's IP address in the Location server HTTP header, though of
course if the server allows the WRITE and MKCOL methods then the server
has greater problems.

Only IIS 5 and 5.1 support the WebDAV methods so these methods only
affect these systems. IIS 5.x and 4.0 are both vulnerable to this issue
if Basic authentication is enabled. (see #NISR05032002A
http://www.nextgenss.com/advisories/iisauth.txt)

Fix Information
***************
To prevent internal IP address disclosure take the following steps.

Open a command prompt and change the current directory to
c:\inetpub\adminscripts or to where the adminscripts can be found.

Run the commands

adsutil set w3svc/UseHostName True
net stop iisadmin /y
net start w3svc

This will cause the IIS server to use the machine's host name rather
than its IP address.

Vendor Status
*************
Microsoft was informed of this issue. They didn't need to take any
action as a suitable work-around is available.

Relevant Pages

  • Re: WM5 can not sync to exchange
    ... I checked all the authentication settings and they are as you requested. ... After running the internet connection wizard I had to uncheck the Require ... On the SBS 2003 Server open the Server Management console. ... Open IIS Manager ...
    (microsoft.public.windows.server.sbs)
  • Re: OWA/RWW question
    ... Thanks, Crina, I think the latter part will help, I had at one point ... changed the IIS server IP address due to a router switch and may not ... entire Web site from the Internet" is selected. ...
    (microsoft.public.windows.server.sbs)
  • RE: Remote Web Workplace not working
    ... Error message: ... Where do you visit RWW, from Internet or LAN? ... Do you have hardware router or firewall between Internet and SBS server? ... Collect IIS Log: ...
    (microsoft.public.windows.server.sbs)
  • Re: Collection of email
    ... Yes Peter you are right IIS is a product I have never used before therfore I ... The server runs a permenant online connection through a ISDN channel 64K. ... Just as a subnote VPOP3 is installed on the server with the Internet and IIS ...
    (microsoft.public.inetserver.iis.smtp_nntp)
  • Re: companyweb
    ... After comparing the IIS metabase from your machine and my test computer, ... Check the settings of the virtual directory companyweb. ... Uncheck Bypass Proxy server for local address. ... and go through the Internet option. ...
    (microsoft.public.windows.server.sbs)