Samsung SW Update Insecure Service Directory ACLs

A privilege escalation vulnerability was identified which can be used by a local user to elevate privileges.

Posted on Sep 10, 2020 | Author: Benjamin Gnahm

Vendor	Samsung, www.samsung.com
Affected Products	SW Update
Affected Versions	<= 2.2.7.22
CVE ID	n/a
OVE ID	OVE-20160530-0004
Severity	High
Author	Benjamin Gnahm (@mitp0sh), Blue Frost Security GmbH

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. Technical 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:\ProgramData\Samsung\SW 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:\Programdata\Samsung\SW Update Service"
C:\Programdata\Samsung\SW Update Service NT AUTHORITY\SYSTEM:(OI)(CI)(ID)F
                                              BUILTIN\Administrators:(OI)(CI)(ID)F
                                              CREATOR OWNER:(OI)(CI)(IO)(ID)F
                                              BUILTIN\Users:(OI)(CI)(ID)R
                                              BUILTIN\Users:(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.

IV. Disclosure Timeline

2016-04-25	Contacted mobile.security@samsung.com and requested a security contact for consumer 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 CVE ID

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