pyLoad is a free and open-source Download Manager written in pure Python. In version 0.5.0b3.dev89, an authenticated path traversal vulnerability exists in the /json/upload endpoint of pyLoad. By manipulating the filename of an uploaded file, an attacker can traverse out of the intended upload directory, allowing them to write arbitrary files to any location on the system accessible to the pyLoad process. This may lead to: Remote Code Execution (RCE), local privilege escalation, system-wide compromise, persistence, and backdoors. This is fixed in version 0.5.0b3.dev90.

Affected: PyPI: pyload-ng

## Summary An **authenticated path traversal vulnerability** exists in the `/json/upload` endpoint of the `pyLoad` By **manipulating the filename of an uploaded file**, an attacker can traverse out of the intended upload directory, allowing them to **write arbitrary files to any location** on the system accessible to the pyLoad process. This may lead to:

* **Remote Code Execution (RCE)** * **Local Privilege Escalation** * **System-wide compromise** * **Persistence and backdoors**

---

### Vulnerable Code

File: [`src/pyload/webui/app/blueprints/json_blueprint.py`](https://github.com/pyload/pyload/blob/df094db67ec6e25294a9ac0ddb4375fd7fb9ba00/src/pyload/webui/app/blueprints/json_blueprint.py#L109)

```python @json_blueprint.route("/upload", methods=["POST"]) def upload(): dir_path = api.get_config_value("general", "storage_folder") for file in request.files.getlist("file"): file_path = os.path.join(dir_path, "tmp_" + file.filename) file.save(file_path) ``` **Issue**: No sanitization or validation on `file.filename`, allowing traversal via `../../` sequences.

### (Proof of Concept)

1. **Clone and install pyLoad from source** (`pip install pyload-ng`):

```bash git clone https://github.com/pyload/pyload cd pyload git checkout 0.4.20 python -m pip install -e . pyload --userdir=/tmp/pyload ```

2. **Or install via pip (PyPi) in virtualenv:**

```bash python -m venv pyload-env source pyload-env/bin/activate pip install pyload==0.4.20 pyload ```…

Affected: PyPI: pyload-ng

## Summary An **authenticated path traversal vulnerability** exists in the `/json/upload` endpoint of the `pyLoad` By **manipulating the filename of an uploaded file**, an attacker can traverse out of the intended upload directory, allowing them to **write arbitrary files to any location** on the system accessible to the pyLoad process. This may lead to:

* **Remote Code Execution (RCE)** * **Local Privilege Escalation** * **System-wide compromise** * **Persistence and backdoors**

---

### Vulnerable Code

File: [`src/pyload/webui/app/blueprints/json_blueprint.py`](https://github.com/pyload/pyload/blob/df094db67ec6e25294a9ac0ddb4375fd7fb9ba00/src/pyload/webui/app/blueprints/json_blueprint.py#L109)

```python @json_blueprint.route("/upload", methods=["POST"]) def upload(): dir_path = api.get_config_value("general", "storage_folder") for file in request.files.getlist("file"): file_path = os.path.join(dir_path, "tmp_" + file.filename) file.save(file_path) ``` **Issue**: No sanitization or validation on `file.filename`, allowing traversal via `../../` sequences.

### (Proof of Concept)

1. **Clone and install pyLoad from source** (`pip install pyload-ng`):

```bash git clone https://github.com/pyload/pyload cd pyload git checkout 0.4.20 python -m pip install -e . pyload --userdir=/tmp/pyload ```

2. **Or install via pip (PyPi) in virtualenv:**

```bash python -m venv pyload-env source pyload-env/bin/activate pip install pyload==0.4.20 pyload ```…