CVE-2025-32755: Jenkins/ssh-slave Docker Image SSH Key Vulnerability

Overview

CVE-2025-32755 is a critical vulnerability in Jenkins/ssh-slave Docker images based on Debian that allows potential system compromise or data leakage. The SSH host keys in these images are generated during image creation, resulting in all containers based on images of the same version using identical SSH host keys. This flaw creates an opportunity for attackers to impersonate build agents, given they can position themselves between the SSH client (typically the Jenkins controller) and the SSH build agent.
This cybersecurity threat poses a significant risk to organizations using these Docker images, especially those leveraging Jenkins for continuous integration/continuous deployment (CI/CD) workflows. The potential for system compromise or data leakage underscores the need for immediate and aggressive mitigation strategies.

Vulnerability Summary

CVE ID: CVE-2025-32755
Severity: Critical (9.1 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: System compromise or data leakage

Affected Products

Product | Affected Versions

Jenkins/ssh-slave Docker image | All Debian-based versions

How the Exploit Works

The exploit takes advantage of the fact that the SSH host keys are generated during image creation, resulting in all Docker containers based on the same Jenkins/ssh-slave image version to use identical SSH host keys. If an attacker can insert themselves into the network path between the SSH client (usually the Jenkins controller) and the SSH build agent, they can impersonate the build agent. This could allow them to gain unauthorized access, potentially leading to system compromise or data leakage.

Conceptual Example Code

The following is a
conceptual
example of how an attacker could exploit this vulnerability:

# Attacker manages to get in between SSH client and build agent
ssh -i duplicate_ssh_key.pem -l jenkins ssh_build_agent_ip
# Once logged in as the build agent, they can execute arbitrary commands
echo 'Compromised system!' > /tmp/exploit.txt

Mitigation Guidance

Users of affected Jenkins/ssh-slave Docker images are encouraged to apply the vendor patch as soon as it becomes available. Until that time, employing a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can serve as a temporary mitigation method. However, these are not foolproof solutions and can only limit the potential damage, not eliminate the risk. Therefore, it is crucial to apply the official patch as soon as possible to completely resolve the vulnerability.