Samsung SW Update 2.2.7.22 Insecure ACLs
Posted on 14 June 2016
Blue Frost Security GmbH https://www.bluefrostsecurity.de/ research(at)bluefrostsecurity.de BFS-SA-2016-003 25-April-2016 ________________________________________________________________________________ Vendor: Samsung, www.samsung.com Affected Products: SW Update Affected Version: <= 2.2.7.22 Vulnerability: Insecure ACLs on SW Update Service Directory CVE ID: n/a OVE ID: OVE-20160530-0004 Vendor ID: SI-6041 ________________________________________________________________________________ I. Impact If the SW Update software is installed on a Windows system, any authenticated user can escalate privileges to become the SYSTEM user by placing a crafted DLL file in the SW Update Service directory and triggering or waiting for the next system reboot. ________________________________________________________________________________ II. Vulnerability Details Samsung consumer computers come with a preinstalled software called SW Update. This software is used to install and update all the necessary drivers and software. The SW Update software installs a Windows service called SWUpdateService which is running as SYSTEM. The service binary SWMAgent.exe is located in the directory "C:ProgramDataSamsungSW Update Service". The ACLs set on this directory allow any authenticated user to create new files as can be seen by the FILE_WRITE_DATA access right below: C:>cacls "c:ProgramdataSamsungSW Update Service" c:ProgramdataSamsungSW Update Service NT AUTHORITYSYSTEM:(OI)(CI)(ID)F BUILTINAdministrators:(OI)(CI)(ID)F CREATOR OWNER:(OI)(CI)(IO)(ID)F BUILTINUsers:(OI)(CI)(ID)R BUILTINUsers:(CI)(ID)(special access:) FILE_WRITE_DATA FILE_APPEND_DATA FILE_WRITE_EA FILE_WRITE_ATTRIBUTES When the service is started it tries to load several non-existing DLL files from the service directory such as MSIMG32.dll, UxTheme.dll or USERENV.dll. A user can place a malicious DLL file with one of the expected names into that directory and wait until the service is restarted. The service can not be restarted by normal users but an attacker could just reboot the system or wait for the next reboot to happen. Afterwards his malicious DLL file would be loaded by the service which is running with SYSTEM privileges which would give the attacker full control over the machine. ________________________________________________________________________________ III. Mitigation To mitigate the issue the ACL on the service directory should be adjusted to prevent normal users from writing to this directory or install the official update to version 2.2.7.24. ________________________________________________________________________________ IV. Disclosure Timeline - 2016-04-25 contacted mobile.security@samsung.com and requested a security contact for consumer desktop / notebook software - 2016-04-29 Samsung confirmed that the advisory was received and that it will be analyzed - 2016-05-27 Requested status update - 2016-05-30 Samsung confirmed that issue "SI-6041" has been fixed starting with version 2.2.7.24 - 2016-05-30 Requested OVE ID: OVE-20160530-0004 was assigned ________________________________________________________________________________ Credit: Bug found by Benjamin Gnahm (@mitp0sh) of Blue Frost Security GmbH. ________________________________________________________________________________ Unaltered electronic reproduction of this advisory is permitted. For all other reproduction or publication, in printing or otherwise, contact research(at)bluefrostsecurity de for permission. Use of the advisory constitutes acceptance for use in an "as is" condition. All warranties are excluded. In no event shall Blue Frost Security be liable for any damages whatsoever including direct, indirect, incidental, consequential, loss of business profits or special damages, even if Blue Frost Security has been advised of the possibility of such damages. Copyright 2016 Blue Frost Security GmbH. All rights reserved. Terms of use apply.
