The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity
Low
AC
The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Privileges Required
None
PR
The attacker is unauthenticated prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction
None
UI
The vulnerable system can be exploited without interaction from any human user, other than the attacker. Examples include: a remote attacker is able to send packets to a target system a locally authenticated attacker executes code to elevate privileges
Scope
Unchanged
S
An exploited vulnerability can only affect resources managed by the same security authority. In the case of a vulnerability in a virtualized environment, an exploited vulnerability in one guest instance would not affect neighboring guest instances.
Confidentiality
High
C
There is total information disclosure, resulting in all data on the system being revealed to the attacker, or there is a possibility of the attacker gaining control over confidential data.
Integrity
High
I
There is a total compromise of system integrity. There is a complete loss of system protection, resulting in the attacker being able to modify any file on the target system.
Availability
High
A
There is a total shutdown of the affected resource. The attacker can deny access to the system or data, potentially causing significant loss to the organization.
QNAPQsyncClientWindows 4.2.1.0602 Privilege EscalationHi @ll,
the executable installer QNAPQsyncClientWindows-4.2.1.0602.exe,
available from <https://www.qnap.com/en/download>, has (like
almost all executable installers) multiple vulnerabilities:
#1: arbitrary (remote) code execution WITH escalation of privilege
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
On a fully patched Windows 7 SP1 it loads and executes the following
Windows system DLLs from its "application directory" instead the
"system directory" %SystemRoot%\System32\:
Version.dll, UXTheme.dll, WinMM.dll, SAMCli.dll, MSACM32.dll,
SFC.dll, SFC_OS.dll, DWMAPI.dll, MPR.dll, ShFolder.dll,
NTMARTA.dll
On other versions of Windows this list changes, but the vulnerable
executable installer always loads and executes some DLLs from its
"application directory".
This weakness is well-known and well-documented:
see <https://cwe.mitre.org/data/definitions/426.html>
and <https://cwe.mitre.org/data/definitions/427.html>
plus <https://capec.mitre.org/data/definitions/471.html>.
See <https://technet.microsoft.com/en-us/library/2269637.aspx>,
<https://msdn.microsoft.com/en-us/library/ff919712.aspx> and
<https://msdn.microsoft.com/en-us/library/ms682586.aspx> for
mitigations of this beginner's error.
For software downloaded with a web browser the "application
directory" is typically the user's "Downloads" directory: see
<https://insights.sei.cmu.edu/cert/2008/09/carpet-bombing-and-directory-poisoning.html>,
<http://blog.acrossecurity.com/2012/02/downloads-folder-binary-planting.html>
and <http://seclists.org/fulldisclosure/2012/Aug/134>
If an attacker places one of the DLLs named above in the users
"Downloads" directory (for example per drive-by download, social
engineering, ...) this vulnerability becomes a remote code
execution WITH escalation of privilege.
Thanks to its "installer detection" Windows' user account control
requests administrative rights for the executable installer, the
DLLs entry points are called with administrative rights -> PWNED!
Demonstration:
1. download <http://home.arcor.de/skanthak/download/SENTINEL.DLL>
and save it as Version.dll in your "Downloads" directory, then
copy it as UXTheme.dll and NTMARTA.dll there too;
2. download
<https://eu1.qnap.com/Storage/Utility/QNAPQsyncClientWindows-4.2.1.0602.exe>
and save it your "Downloads" directory;
3. execute QNAPQsyncClientWindows-4.2.1.0602.exe from your
"Downloads" directory;
4. notice the message boxes displayed from ShFolder.dll etc. placed
in step 1.
#2: unsafe %TEMP% directory
~~~~~~~~~~~~~~~~~~~~~~~~~~~
It creates a subdirectory ns<letter><random_hex_value>.tmp in %TEMP%
where it extracts multiple DLLs to and executes them.
This subdirectory inherits the access rights of its parent %TEMP%,
so an unprivileged attacker^Wuser can replace the DLLs between their
creation and execution, again resulting in arbitrary code execution
with escalation of privilege.
See <https://cwe.mitre.org/data/definitions/377.html> and
<https://cwe.mitre.org/data/definitions/379.html> for this
well-known and well-documented weakness.
Demonstration:
create the following batch script
:WAIT
@If Not Exist "%TEMP%\ns*.tmp" Goto :WAIT
For /D %%! In ("%TEMP%\ns*.tmp") Do Set foobar=%%!
For %%! In ("%foobar%\*.dll") Do Copy /Y "%USERPROFILE%\Downloads\Version.dll" "%%!"
and start it, then rerun QNAPQsyncClientWindows-4.2.1.0602.exe
Additionally see <http://seclists.org/fulldisclosure/2015/Dec/32>,
<http://seclists.org/fulldisclosure/2015/Oct/109>,
<http://seclists.org/fulldisclosure/2015/Nov/101> and
<http://seclists.org/fulldisclosure/2015/Dec/86>,
plus <https://skanthak.homepage.t-online.de/!execute.html>
and <https://skanthak.homepage.t-online.de/sentinel.html>
FIX:
~~~~
* DON'T build executable installers at all!
* Provide either a *.MSI or a *.CAB plus an *.INF
* NEVER use executable installers at all!
* Add the NTFS ACE "(D;OIIO;WP;;;WD)" meaning
"deny execution of files in this directory and all subdirectories"
to the NTFS ACL of every %TEMP% directory!
JFTR: when execution in %TEMP% is denied, the defective
installer display a dialog box with the blatant lie
"QSync is running.
Click [OK] to close QSync and continue the installation,
or [Cancel] to terminate the process."
and repeats it after clicking [OK], over and over again.
The only way to exit this loop is [Cancel]
stay tuned
Stefan Kanthak
Timeline:
~~~~~~~~~
2017-07-29 vulnerability report sent to vendor
automated response from vendor:
"Our team will get back to you as soon as possible."
no more reaction from vendor
2017-08-07 vulnerability report resent to vendor
automated response from vendor:
"Our team will get back to you as soon as possible."
no more reaction from vendor
2017-08-16 report published
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