CVE-2021-20758
📋 TL;DR
This CSRF vulnerability in Cybozu Garoon allows authenticated attackers to trick administrators into performing unintended actions by exploiting their active sessions. It affects all Garoon users with administrator accounts. Attackers can perform arbitrary operations through the administrator interface.
💻 Affected Systems
- Cybozu Garoon
📦 What is this software?
Garoon by Cybozu
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the Garoon instance - attackers could create new admin accounts, modify system settings, access sensitive data, or disrupt business operations.
Likely Case
Unauthorized configuration changes, data exposure, or privilege escalation leading to further attacks within the system.
If Mitigated
Limited impact with proper CSRF protections, session management, and administrator awareness training.
🎯 Exploit Status
CSRF attacks are well-understood and easy to implement. Requires attacker to be authenticated and trick administrator into clicking malicious link.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 5.0.3 and later
Vendor Advisory: https://cs.cybozu.co.jp/2021/007206.html
Restart Required: Yes
Instructions:
1. Backup your Garoon instance. 2. Download and install Garoon 5.0.3 or later from Cybozu. 3. Apply the update through the Garoon administration interface. 4. Restart the Garoon service. 5. Verify the update was successful.
🔧 Temporary Workarounds
Implement CSRF Tokens
allAdd anti-CSRF tokens to all administrative forms and validate them server-side.
SameSite Cookie Attribute
allSet SameSite=Strict or SameSite=Lax attributes on session cookies to prevent cross-site requests.
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to detect and block CSRF attempts
- Require re-authentication for sensitive administrative actions and implement multi-factor authentication
🔍 How to Verify
Check if Vulnerable:
Check Garoon version in administration interface. If version is between 4.0.0 and 5.0.2 inclusive, system is vulnerable.Check Version:
Check version in Garoon administration panel under System Settings > System InformationVerify Fix Applied:
Verify Garoon version is 5.0.3 or later in administration interface. Test administrative forms for CSRF token implementation.📡 Detection & Monitoring
Log Indicators:
- Multiple administrative actions from same session in rapid succession
- Administrative actions from unexpected IP addresses or user agents
Network Indicators:
- HTTP POST requests to administrative endpoints without proper referrer headers or CSRF tokens
SIEM Query:
source="garoon_logs" AND (action="admin_" OR user_role="admin") AND count() > threshold