CVE-2023-41939
📋 TL;DR
The Jenkins SSH2 Easy Plugin vulnerability allows users who previously had optional permissions (like Overall/Manage) to retain access to functionality they should no longer have. This occurs because the plugin fails to verify that configured permissions are actually enabled. Organizations using Jenkins with the SSH2 Easy Plugin version 1.4 or earlier are affected.
💻 Affected Systems
- Jenkins SSH2 Easy Plugin
📦 What is this software?
Ssh2 Easy by Jenkins
⚠️ Risk & Real-World Impact
Worst Case
Former administrators or privileged users could regain elevated access, potentially allowing them to modify Jenkins configurations, install malicious plugins, access sensitive data, or disrupt CI/CD pipelines.
Likely Case
Users who previously had optional permissions but had them revoked could access functionality they're no longer authorized for, potentially leading to unauthorized configuration changes or data access.
If Mitigated
With proper access controls and monitoring, impact is limited to potential unauthorized access by users who previously had permissions, which can be detected through audit logs.
🎯 Exploit Status
Exploitation requires a user account that previously had optional permissions. The vulnerability is in permission verification logic, making exploitation straightforward for users with the right conditions.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.5 or later
Vendor Advisory: https://www.jenkins.io/security/advisory/2023-09-06/#SECURITY-3064
Restart Required: Yes
Instructions:
1. Update Jenkins SSH2 Easy Plugin to version 1.5 or later via Jenkins Plugin Manager. 2. Restart Jenkins to apply the update. 3. Verify the plugin version in Jenkins plugin management interface.
🔧 Temporary Workarounds
Disable SSH2 Easy Plugin
allTemporarily disable the vulnerable plugin if immediate patching isn't possible
Navigate to Jenkins > Manage Jenkins > Manage Plugins > Installed tab > Find SSH2 Easy Plugin > Disable
Restrict User Permissions
allReview and tighten user permissions, especially for users who previously had optional permissions
Navigate to Jenkins > Manage Jenkins > Manage and Assign Roles > Review all user permissions
🧯 If You Can't Patch
- Disable the SSH2 Easy Plugin entirely until patching is possible
- Implement strict access controls and monitor for unusual permission usage patterns
🔍 How to Verify
Check if Vulnerable:
Check Jenkins plugin manager for SSH2 Easy Plugin version. If version is 1.4 or earlier, the system is vulnerable.Check Version:
Navigate to Jenkins > Manage Jenkins > Manage Plugins > Installed tab > Find SSH2 Easy PluginVerify Fix Applied:
Verify SSH2 Easy Plugin version is 1.5 or later in Jenkins plugin manager and test that users with revoked permissions cannot access restricted functionality.📡 Detection & Monitoring
Log Indicators:
- Audit logs showing users accessing functionality they shouldn't have permissions for
- Access logs showing users with revoked permissions performing privileged actions
Network Indicators:
- Unusual SSH connections to Jenkins from users with limited permissions
SIEM Query:
source="jenkins" AND (event="permission_violation" OR user_action="unauthorized_access")