CVE-2015-3442 Authentication Bypass in Xpert.Line Version 3.0

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# COMPASS SECURITY ADVISORY
# http://www.csnc.ch/en/downloads/advisories.html
#
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# Product:      Xpert.Line
# Vendor:       Soreco AG [1]
# CVE ID:       CVE-2015-3442
# Subject:      Authentication Bypass
# Risk:         Critical
# Effect:       Remotely exploitable
# Authors:      Alessandro Zala (alessandro.zala@csnc.ch)
#               Andreas Hunkeler (andreas.hunkeler@csnc.ch)
# Date:         06.03.2015
#
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Introduction:
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The Xpert.Line software [2] is a Human Resources Management solution that helps
companies administrating information assets of their employees. It manages
all the private information about the employees. Compass Security [3] found a
vulnerability that allows an attacker to impersonate other users by only
knowing the username of the person. With this flaw a user can bypass the
authentication mechanism and achieve highest privileges to access personal
information like the salary of any employee or manipulate security settings
(e.g. accounts) of the application.

Affected:
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Xpert.Line Version 3.0 (Xpert.Center). Other versions have not been tested.

Vulnerability Description:
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Xpert.Line has several authentication mechanisms to authenticate the user to the
application. One of the authentication mechanisms relies only on client-side
functionalities. When the Xpert.Line Windows client is started, it first
retrieves the username of the current logged-in Windows user by using an API
call to "getUserNameA" from the Windows built-in library "advapi32.dll". This
information is then sent to the server to authenticate the user to Xpert.Line
and it is also used for all subsequent requests to the server.

Impact:
-------
A malicious user can impersonate any user by intercepting the above mentioned
API call to "getUserNameA" in "advapi32.dll" and change the value returned to
an arbitrary name. This allows impersonating higher privileged users to access
sensitive information like salary information or to create new administrator
accounts.

Workaround / Fix:
-----------------
The affected authentication mechanism can be deactivated. The vendor currently
is not willing to remove this authentication mechanism. Instead, vendor offers
more secure authentication mechanisms and considers this a configuration issue.

To deactivate the affected unsecure authentication method do the following:
1. Go to Xpert.Security
2. Got to "change environment" settings
3. Change the authentication type to a secure setting (e.g. LDAPs)

Source: Xpert.Security LDAP documentation, received from vendor on 06.03.2015

Timeline:
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29.01.2015: Vulnerability detected
19.02.2015: Initial contact, conference call with vendor
03.03.2015: CVE ID requested
03.03.2015: Request vendor's security contact information (info@soreco.ch)
05.03.2015: 2nd Request vendor's security contact information (info@soreco.ch)
05.03.2015: Vendor notification with technical details to contact person via
            secured channel
05.03.2015: Conference call with vendor discussing finding and next steps
06.03.2015: 2nd conference call with vendor to discuss workaround and
            publication, vendor approved immediate publication
29.04.2015: CVE ID received: CVE-2015-3442
02.07.2015: Public disclosure

Very positive was the handling of the notification. The vendor was very
responsive to our notification and was very willing to cooperate with us.

References:
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[1]   http://www.sorecoweb.ch/home/
[2]   http://www.xpertline.ch/
[3]   http://www.csnc.ch/en/