CVE-2025-64136
📋 TL;DR
A CSRF vulnerability in Jenkins Themis Plugin 1.4.1 and earlier allows attackers to trick authenticated users into making unintended requests to attacker-controlled HTTP servers. This affects Jenkins instances with the vulnerable Themis plugin installed, potentially exposing internal Jenkins data or credentials to external attackers.
💻 Affected Systems
- Jenkins Themis Plugin
📦 What is this software?
Themis by Jenkins
⚠️ Risk & Real-World Impact
Worst Case
Attackers could exfiltrate Jenkins credentials, configuration data, or sensitive build artifacts to external servers under their control, leading to full Jenkins compromise or data breach.
Likely Case
Attackers could redirect Jenkins requests to malicious servers, potentially harvesting session tokens, API keys, or other sensitive information from authenticated users.
If Mitigated
With proper CSRF protections and network segmentation, impact is limited to unsuccessful connection attempts to external servers.
🎯 Exploit Status
Exploitation requires tricking authenticated users into visiting malicious web pages while logged into Jenkins.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Jenkins Themis Plugin 1.4.2 or later
Vendor Advisory: https://www.jenkins.io/security/advisory/2025-10-29/#SECURITY-3517
Restart Required: No
Instructions:
1. Navigate to Jenkins Manage Plugins. 2. Update Themis Plugin to version 1.4.2 or later. 3. No restart required for plugin updates in Jenkins.
🔧 Temporary Workarounds
Disable Themis Plugin
allTemporarily disable the vulnerable plugin until patching is possible
Navigate to Jenkins -> Manage Jenkins -> Manage Plugins -> Installed tab -> Find Themis Plugin -> Disable
Implement CSRF Protection Headers
allAdd CSRF protection headers to Jenkins reverse proxy configuration
Add 'X-Content-Type-Options: nosniff' and 'X-Frame-Options: DENY' headers to Jenkins proxy configuration
🧯 If You Can't Patch
- Segment Jenkins network to prevent outbound connections to untrusted servers
- Implement strict Content Security Policy (CSP) headers to restrict external connections
🔍 How to Verify
Check if Vulnerable:
Check Jenkins plugin manager for Themis Plugin version 1.4.1 or earlierCheck Version:
Navigate to Jenkins -> Manage Jenkins -> Manage Plugins -> Installed tab -> Find Themis PluginVerify Fix Applied:
Verify Themis Plugin version is 1.4.2 or later in Jenkins plugin manager📡 Detection & Monitoring
Log Indicators:
- Unusual outbound HTTP connections from Jenkins to unknown domains
- Failed CSRF token validation attempts in Jenkins logs
Network Indicators:
- Unexpected HTTP traffic from Jenkins servers to external IPs
- Jenkins making connections to non-whitelisted domains
SIEM Query:
source="jenkins.log" AND ("CSRF" OR "Themis" OR "outbound connection")