[SYSS-2015-001] Kaspersky Endpoint Security - Authentication Bypass

From: matthias.deeg@syss.de
To: bugtraq@securityfocus.com
Subject: [SYSS-2015-001] Kaspersky Endpoint Security - Authentication Bypass

Hash: SHA512

Advisory ID: SYSS-2015-001
Product: Kaspersky Endpoint Security for Windows (KES)
Manufacturer: Kaspersky Lab ZAO
Affected Version(s):,
Tested Version(s):,
Vulnerability Type: Authentication Bypass Using an Alternate Path or 
                    Channel (CWE-288)
Risk Level: Medium
Solution Status: Fixed
Vendor Notification: 2015-02-19
Solution Date: 2015-10-01
Public Disclosure: 2015-10-01
CVE Reference: Not yet assigned
Authors of Advisory: Sven Freund and Matthias Deeg (SySS GmbH)



Kaspersky Endpoint Security for Windows provides centralized protection
of Windows workstations and Windows servers from malware, potentially
dangerous programs and network attacks. It includes features such as
data encryption functionality for encrypting hard drives and removable
devices, centralized vulnerability flagging and virtual machine support
(see [1]).


Vulnerability Details:

The Kaspersky Endpoint Security for Windows software allows users to
disable the offered protection by entering a so-called unload password.
Beside the graphical user interface (GUI) authentication, it is also
possible to manually deactivate the protection over the command-line
interface using the Kaspersky software tool avp.exe.

By analyzing the password-based authentication for unloading the
Kaspersky Endpoint Security for Windows protection, the SySS GmbH found
out, that the password comparison is done within the process avp.exe,
which runs or can be run in the context of the current Windows user,
who can also be a standard, limited user.

This fact allows a further analysis and the manipulation of the password
comparison during runtime without administrative privileges, as every 
user is able to debug and manipulate the processes running with her user

In order to bypass the password-based authentication to deactivate the 
protection of Kaspersky Endpoint Security for Windows in an unauthorized
manner, an attacker only has to patch this password comparison, so that 
it always returns true, for example by comparing the correct unload
password with itself or by modifying the program control flow.

The SySS GmbH also found out, that by modifying the software tool 
avp.exe, the Kaspersky Endpoint Security for Windows can also be
deactivated completely even when no password was set for protecting
administrative functions. The intended behavior of the software tool
avp.exe in this case is to deny access to the requested function, for
example "exit", due to a disabled password protection.

Thus, a limited Windows user or malware running in the context of such a
user is able to unload Kaspersky Endpoint Security for Windows in an
unauthorized manner regardless of the configured password protection.


Proof of Concept (PoC):

The SySS GmbH developed a proof-of-concept software tool named UnloadKES
for deactivating Kaspersky Endpoint Security for Windows in an
unauthorized manner.

The following output exemplarily shows a successful deactivation of
Kaspersky Endpoint Security for Windows:

               /    _____       _____ _____                                 \
              /    /  ___|     /  ___/  ___|                                 \
             |     \ `--. _   _\ `--.\ `--.                                   |
             |      `--. \ | | |`--. \`--. \                                  |
             |     /\__/ / |_| /\__/ /\__/ /                                  |
              \    \____/ \__, \____/\____/   ... unloads KES!               /
               \          __/ |                                             /
               /         |___/    _________________________________________/
              / _________________/
        (__) /_/
 / |____||
*  ||   ||
   ^^   ^^
SySS Unload KES v1.0 by Sven Freund & Matthias Deeg - SySS GmbH (c) 2015

[+] Found location of the executable file avp.exe
[+] Created new instance of the Kaspersky Endpoint Security process avp.exe
[+] The Kaspersky Endpoint Security process was patched successfully.
    Kaspersky Endpoint Security will now exit without a password.



According to information by Kaspersky, the described security issue has
been fixed in newer software releases.

Please contact the manufacturer for further information or support.


Disclosure Timeline:

2015-02-19: Vulnerability reported to manufacturer
2015-02-19: Manufacturer acknowledges e-mail with SySS security advisory          
2015-03-17: Rescheduling of the publication date in agreement with the
2015-04-14: Rescheduling of the publication date in agreement with the
2015-05-21: Manufacturer asks for PoC software tool
2015-05-22: SySS sent PoC software tool to manufacturer
2015-09-28: SySS asks for further information about software fix
2015-10-01: Public release of security advisory on agreed publication



[1] Product Web site for Kaspersky Endpoint Security for Windows
[2] SySS Security Advisory SYSS-2015-001
[3] SySS Responsible Disclosure Policy



This security vulnerability was found by Sven Freund and Matthias Deeg 
of the SySS GmbH.

E-Mail: sven.freund (at) syss.de
Public Key: https://www.syss.de/fileadmin/dokumente/Materialien/PGPKeys/Sven_Freund.asc
Key fingerprint = DCDB 7627 C1E3 9CE8 62DF 2666 8A5F A853 415D 46DC

E-Mail: matthias.deeg (at) syss.de
Public Key: https://www.syss.de/fileadmin/dokumente/Materialien/PGPKeys/Matthias_Deeg.asc
Key fingerprint = D1F0 A035 F06C E675 CDB9 0514 D9A4 BF6A 34AD 4DAB



The information provided in this security advisory is provided "as is" 
and without warranty of any kind. Details of this security advisory may 
be updated in order to provide as accurate information as possible. The
latest version of this security advisory is available on the SySS Web 



Creative Commons - Attribution (by) - Version 3.0
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