I have updated my original advisory to reflect a
better solution due to feedback on the vuln-watch
list.

The attached advisory can also be found at:
http://hypoclear.cjb.net/hypo_linksys_advisory.txt

hypoclear - hypoclearjungle.net -
http://hypoclear.cjb.net

---

        [[:UPDATE hypoclear security advisory
UPDATE:]]

Update Note: Thanks to the guys on the vuln-watch
list who helped
             with a better solution!


Vendor : Linksys | http://www.linksys.com/
Product : EtherFast 4-Port Cable/DSL Router
Category : Design Flaw
Date : 08-02-01
Update : 08-02-01

CONTENTS
1. Overview
2. Details
3. "Exploit"
4. Possible Solution
5. Vendor Response
6. Contact
7. Disclaimer


1. Overview:

The Linksys "EtherFast 4-Port Cable/DSL Router" is
subject to a security flaw in its
design. Passwords for the router and the users
ISP account can be viewed in the HTML
source code stored on the router.



2. Details:

The login passwords for both the router and the
users ISP are passed to the routers
configuration pages. While they cannot be viewed
directly in the browser window the
passwords are in "cleartext" if viewed via the
HTML source code. This may lead to a
compromise of the router and the users ISP
account. The pages in question are index.htm,
which contains the users ISP logon and password,
and Passwd.htm, which contains the
password for the router.

If combined with a "sniffer" attack the source
code (with passwords) can be viewed during
transmission to the administrators browser.

(Note: The transmissions can only be "sniffed"
within the LAN behind the router.)



3. "Exploit"

There is no exploit code needed to exploit this
vulnerability. The passwords are stored
and transmitted in "cleartext" within the HTML
source. The passwords can easily be viewed
by sniffing the ethernet when an Administrator
logs in and views the offending pages.

Sections of offending code (code formatted for
easier viewing):

On index.htm:

--- code cut ---
<b>User Name: &nbsp;</b></font><input
name=pppoeUName size=20

maxlength=63 value=USERS_ISP_LOGIN_HERE>

</td></tr><tr><th bgcolor=6666cc>&nbsp;</th>
<td>&nbsp; &nbsp; <font face=verdana
size=2><b>Password: &nbsp;
&nbsp;</b></font><input type=password
name=pppoePWD size=20 maxlength=63

value=USERS_ISP_PASSWORD_HERE></td>

--- end code cut ---


On Passwd.htm:

--- code cut ---
<br>Router Password: &nbsp;</th><td> <br> &nbsp;
<input type=password name=sysPasswd size=25
maxlength=63

value=ROUTER_PASSWORD_HERE>

<font color=blue face=Arial size=2>
(Enter New Password)</td></tr> <tr><th
bgcolor=6666cc align=right><font
color=white face=Arial size=2>&nbsp;</th> <td>
&nbsp;
<input type=password name=sysPasswdConfirm size=25
maxlength=63

value=CONFIRM_OF_ROUTER_PASSWORD_HERE>

--- end code cut ---



4. Possible Solution

A suggested solution for this problem is to not
transmit the passwords to the offending
pages. Instead, keep them stored in the router,
and only allow for the update of
passwords on the pages (if desired by the user).

This particular solution is not possible without a
vendor patch.
There has been no resopnse from Linksys.


Another solution has been given by weld on the
vuln-watch list.

He states:
"I would say the solution is to only admin the
router from a workstation that
is directly connected to one of the switch ports
and to add a static arp cache
entry for the router on the workstation. That
will deny any arp cache poisioning
which would work to sniff across the switch."



5. Vendor Response

07-23-01: Sent problem to Linksys via the email
address supportlinksys.com.
          No security email address could be found
on their web-site.
          The email stated the problem and a
possible solution.

07-30-01: No response was givin to the initial
email, so a second email was sent.
          The email stated that I had already
tried to contact them over a week ago,
          and if no response was givin in the next
few days I would release the advisory.

08-02-01: At the time of the release of this
advisory, Linksys has not responded.



6. Contact

Written by hypoclear.
email : hypoclearjungle.net
home page : http://hypoclear.cjb.net


7. Disclaimer

This advisory remains the property of hypoclear.
This advisory can be freely distributed in any
form.
If this advisory is distributed it must remain in
its entirety.

This and all of hypoclear's releases fall under
his disclaimer,
which can be found at:
http://hypoclear.cjb.net/hypodisclaim.txt

• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]