Visit our newest sister site!
Hundreds of free aircraft flight manuals
Civilian • Historical • Military • Declassified • FREE!


TUCoPS :: Cisco :: tb12151.htm

Local privilege escalation vulnerability in Cisco VPN client



Local privilege escalation vulnerability in Cisco VPN client
Local privilege escalation vulnerability in Cisco VPN client



======Summary
======Name: Permissively-ACLed cvpnd.exe allows interactive users to run
arbitrary binaries with Local System Privileges
Release Date: 16 August 2007
Reference: NGS00503
Discover: Dominic Beecher  
Vendor: Cisco
Vendor Reference: cisco-sa-20070815-vpnclient
Systems Affected:  All versions up to but not including 5.0.01.0600
Risk: High
Status: Published

=======TimeLine
=======Discovered: 18 May 2007
Released: 22 May 2007
Approved: 11 June 2007
Reported: 23 May 2007
Fixed: 15 August 2007
Published: 16 August 2007

==========Description
==========Impact: locally logged-on users of affected hosts can cause arbitrary
binaries to be executed in the context of Local System. This effectively
compromises the host.

================Technical Details
================Cisco's VPN client for Windows installs a Windows service, the "Cisco
Systems, Inc. VPN Service" or CVPND, whose associated binary is
C:\Program Files\Cisco Systems\VPN Client\cvpnd.exe. By default, the
CVPND service runs as Local System.

SERVICE_NAME: CVPND
        TYPE               : 110  WIN32_OWN_PROCESS (interactive)
        START_TYPE         : 2   AUTO_START
        ERROR_CONTROL      : 0   IGNORE
        BINARY_PATH_NAME   : "C:\Program Files\Cisco Systems\VPN
Client\cvpnd.exe"
        LOAD_ORDER_GROUP   :
        TAG                : 0
        DISPLAY_NAME       : Cisco Systems, Inc. VPN Service
        DEPENDENCIES       : TCPIP
        SERVICE_START_NAME : LocalSystem

Interactive Users (i.e. those who have logged on locally) are granted
Modify permissions to cvpnd.exe (and its parent directory), denoted by
NT AUTHORITY\INTERACTIVE:C in the cacls output below.

C:\Program Files\Cisco Systems\VPN Client\cvpnd.exe
                                            NT AUTHORITY\INTERACTIVE:C
                                            BUILTIN\Users:R
                                            BUILTIN\Power Users:C
                                            BUILTIN\Administrators:F
                                            NT AUTHORITY\SYSTEM:F
                                            BUILTIN\Administrators:F

This allows normal users who have logged on to a susceptible host to
move cvpnd.exe to another location, and substitute another binary for
cvpnd.exe. When the CVPND service restarts (e.g. on reboot), the
replaced cvpnd.exe will run in the context of Local System. This
effectively escalates users' privileges, thereby compromising the host.

==============Fix Information
==============Upgrade to a fixed version of the Cisco VPN client: see Cisco's advisory
at the URL below for more details.

http://www.cisco.com/warp/public/707/cisco-sa-20070815-vpnclient.shtml 

Alternatively, as a workaround, revoke access rights for NT
AUTHORITY\INTERACTIVE from cvpnd.exe, e.g.:

C:\Program Files\Cisco Systems\VPN Client>cacls cvpnd.exe /E /R "NT
AUTHORITY\INTERACTIVE"


--
NGSSoftware Insight Security Research
http://www.ngssoftware.com/ 
http://www.databasesecurity.com/ 
http://www.nextgenss.com/ 
+44(0)208 401 0070

--
E-MAIL DISCLAIMER

The information contained in this email and any subsequent
correspondence is private, is solely for the intended recipient(s) and
may contain confidential or privileged information. For those other than
the intended recipient(s), any disclosure, copying, distribution, or any
other action taken, or omitted to be taken, in reliance on such
information is prohibited and may be unlawful. If you are not the
intended recipient and have received this message in error, please
inform the sender and delete this mail and any attachments.

The views expressed in this email do not necessarily reflect NGS policy.
NGS accepts no liability or responsibility for any onward transmission
or use of emails and attachments having left the NGS domain.

NGS and NGSSoftware are trading names of Next Generation Security
Software Ltd. Registered office address: 52 Throwley Way, Sutton, SM1
4BF with Company Number 04225835 and VAT Number 783096402


TUCoPS is optimized to look best in Firefox® on a widescreen monitor (1440x900 or better).
Site design & layout copyright © 1986-2014 AOH