CVE-2021-39115
📋 TL;DR
This CVE allows remote attackers with Jira Administrator access to execute arbitrary Java code or system commands via server-side template injection in Jira Service Management's Email Template feature. It affects Jira Service Management Server and Data Center installations. Attackers need administrative credentials but can achieve full system compromise.
💻 Affected Systems
- Atlassian Jira Service Management Server
- Atlassian Jira Service Management Data Center
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system takeover with attacker gaining root/system-level access, data exfiltration, lateral movement, and persistent backdoor installation.
Likely Case
Privileged attacker executes arbitrary commands to steal sensitive data, modify configurations, or disrupt service availability.
If Mitigated
Attack limited to administrative users only, with proper access controls preventing unauthorized administrative access.
🎯 Exploit Status
Exploitation requires Jira Administrator credentials but uses simple template injection techniques. Public exploit details exist.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.13.9 or 4.18.0 and later
Vendor Advisory: https://jira.atlassian.com/browse/JSDSERVER-8665
Restart Required: Yes
Instructions:
1. Backup your Jira instance. 2. Download and install Jira Service Management version 4.13.9 or 4.18.0+. 3. Follow Atlassian upgrade documentation. 4. Restart the service. 5. Verify the upgrade completed successfully.
🔧 Temporary Workarounds
Restrict Jira Administrator Access
allLimit Jira Administrator accounts to only essential personnel and implement strong authentication controls.
Disable Email Template Feature
allTemporarily disable or restrict access to the Email Template functionality if not required.
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Jira instances from critical systems
- Enforce multi-factor authentication for all Jira Administrator accounts and monitor their activity closely
🔍 How to Verify
Check if Vulnerable:
Check Jira Service Management version via Admin → System → System Info. If version is below 4.13.9 or between 4.14.0-4.17.x, you are vulnerable.Check Version:
Check via web interface at /secure/admin/ViewApplicationProperties.jspa or examine atlassian-jira.log for version information.Verify Fix Applied:
After patching, verify version is 4.13.9 or 4.18.0+ in System Info. Test email template functionality to ensure it works without errors.📡 Detection & Monitoring
Log Indicators:
- Unusual template rendering errors in application logs
- Suspicious administrative activity patterns
- Unexpected Java class loading or command execution
Network Indicators:
- Unusual outbound connections from Jira server
- Traffic to unexpected ports or external IPs
SIEM Query:
source="jira.log" AND ("template injection" OR "freemarker.template" OR suspicious_admin_activity)