CVE-2020-0796 PoC — 微软 Microsoft SMBv3 缓冲区错误漏洞

Description

Scanner for CVE-2020-0796 - A SMBv3.1.1 + SMB compression RCE 

介绍

# SMBGhost
This repository contains my scanner script which lets you know whether your server uses SMBv3.1.1 and has SMB compression enabled. Ultimately, this means you are vulnerable to [CVE-2020-0796](https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2020-0796). At this point of time a security patch was released, please make sure to update!  
It also offers a fully documented packet structure which can be utilized for further investigations targeting the SMB protocol.  
Keep in mind that this scanner will only tell you whether you have SMBv3.1.1 and SMB compression enabled or not. It will mark a patched system as vulnerable as well!

## Usage
The module has extensive logging and requires the library `hexdump` which you can install with `pip3 install --user hexdump`. If you don't want logging you can use the script in `logless_scanner.py`.

```
python3 .\scanner.py 127.0.0.1 445
NetBIOS (4): 000000c0
Header (64): fe534d42400000000000000000001f00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
Negotiation (128): 24000800010000007f000000000000000000000000000000000000007800000002000000020210022202240200030203100311030000000001002600000000000100200001000100000000000000000000000000000000000000000000000000000000000000000003000a000000000001000000010000000100000000000000
Packet (196): 000000c0fe534d42400000000000000000001f0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000024000800010000007f000000000000000000000000000000000000007800000002000000020210022202240200030203100311030000000001002600000000000100200001000100000000000000000000000000000000000000000000000000000000000000000003000a000000000001000000010000000100000000000000
```

Some output was ommited for the sake of a cleaner README. If you are vulnerable, the script will output the following text:

```
SMB version 0x311 with context 0x2 was found which indicates SMBv3.1.1 is being used and SMB compression is enabled, therefore being vulnerable to CVE-2020-0796!
```

![vulnerable](vulnerable.png)

## Workarounds
If you are unable to install the security patch provided by Microsoft please consider disabling SMB compression using the following command:

```powershell
Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters" DisableCompression -Type DWORD -Value 1 -Force
```

However, this will not protect you from getting exploited if you are the client connecting to an exploited machine.

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