CVE-2026-20711
📋 TL;DR
A cross-site scripting vulnerability in the email function of Cybozu Garoon allows attackers to inject malicious scripts that can reset arbitrary users' passwords. This affects organizations using Cybozu Garoon versions 5.0.0 through 6.0.3. The vulnerability requires user interaction but can lead to account compromise.
💻 Affected Systems
- Cybozu Garoon
⚠️ Risk & Real-World Impact
Worst Case
Attackers could reset administrator passwords, gain full system access, and potentially compromise the entire Garoon deployment and connected systems.
Likely Case
Targeted attacks against specific users to reset their passwords, leading to unauthorized access to sensitive business information and email communications.
If Mitigated
With proper input validation and output encoding, the XSS payload would be neutralized, preventing password reset functionality abuse.
🎯 Exploit Status
Exploitation requires user interaction (clicking a malicious link) but the XSS payload construction is straightforward for attackers with basic web security knowledge.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 6.0.4 and later
Vendor Advisory: https://kb.cybozu.support/article/39081/
Restart Required: Yes
Instructions:
1. Backup your Garoon installation and database. 2. Download Garoon 6.0.4 or later from Cybozu support portal. 3. Follow the official upgrade procedure documented in Cybozu's upgrade guide. 4. Restart the Garoon service after upgrade completion.
🔧 Temporary Workarounds
Input Validation Enhancement
allImplement additional input validation for email fields to reject suspicious characters and scripts.
Not applicable - requires code modification
Content Security Policy
allImplement strict CSP headers to prevent execution of inline scripts and restrict script sources.
Add 'Content-Security-Policy: script-src 'self'' to web server configuration
🧯 If You Can't Patch
- Implement web application firewall rules to block XSS patterns in email function requests
- Disable the vulnerable email function if not business-critical and monitor for alternative attack vectors
🔍 How to Verify
Check if Vulnerable:
Check Garoon version via Administration > System Information. If version is between 5.0.0 and 6.0.3 inclusive, system is vulnerable.Check Version:
Not applicable - check via Garoon web interface Administration > System InformationVerify Fix Applied:
After patching, verify version is 6.0.4 or later and test email function with basic XSS payloads to confirm they are properly sanitized.📡 Detection & Monitoring
Log Indicators:
- Unusual password reset requests
- Email function requests containing script tags or JavaScript code
- Multiple failed login attempts following password resets
Network Indicators:
- HTTP requests to email endpoints containing suspicious script patterns
- Unusual traffic patterns to password reset functionality
SIEM Query:
source="garoon_logs" AND (message="password reset" OR message="email function") AND (message CONTAINS "<script>" OR message CONTAINS "javascript:")