CVE-2021-42086
📋 TL;DR
This vulnerability allows authenticated Agent accounts in Zammad to escalate privileges to Administrator level by modifying account data through crafted requests. It affects all Zammad installations running versions before 4.1.1 where Agent accounts exist.
💻 Affected Systems
- Zammad
📦 What is this software?
Zammad by Zammad
⚠️ Risk & Real-World Impact
Worst Case
An attacker with Agent credentials gains full administrative control over the Zammad instance, allowing them to access all tickets, modify system settings, create/delete users, and potentially compromise the underlying server.
Likely Case
Malicious or compromised Agent accounts escalate to Administrator privileges, enabling unauthorized access to sensitive customer data and system configuration.
If Mitigated
With proper access controls and monitoring, privilege escalation attempts are detected and blocked before successful exploitation.
🎯 Exploit Status
Exploitation requires authenticated Agent access. The vulnerability is in the account modification logic, making it relatively straightforward to exploit once authenticated.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.1.1
Vendor Advisory: https://zammad.com/en/advisories/zaa-2021-09
Restart Required: Yes
Instructions:
1. Backup your Zammad instance and database. 2. Update to Zammad 4.1.1 or later using your deployment method (package manager, Docker, manual). 3. Restart Zammad services. 4. Verify the update completed successfully.
🔧 Temporary Workarounds
Restrict Agent Account Permissions
allTemporarily reduce Agent account privileges to minimum required functions while planning upgrade.
Enhanced Monitoring
allImplement strict monitoring of account modification activities and privilege changes.
🧯 If You Can't Patch
- Implement strict access controls and monitoring for all Agent accounts
- Consider temporarily disabling non-essential Agent accounts until patching is possible
🔍 How to Verify
Check if Vulnerable:
Check Zammad version via web interface Admin > System > About, or run: grep 'VERSION' /path/to/zammad/config/initializers/version.rbCheck Version:
grep 'VERSION' /path/to/zammad/config/initializers/version.rb 2>/dev/null || echo 'Check web interface Admin > System > About'Verify Fix Applied:
Confirm version is 4.1.1 or later and test that Agent accounts cannot modify privilege levels.📡 Detection & Monitoring
Log Indicators:
- Unusual account modification requests from Agent accounts
- Privilege escalation attempts in authentication logs
- Multiple failed privilege modification attempts
Network Indicators:
- HTTP POST requests to account modification endpoints from Agent accounts
SIEM Query:
source="zammad" AND (event_type="account_update" OR event_type="privilege_change") AND user_role="agent"