CVE-2024-50599
📋 TL;DR
A reflected Cross-Site Scripting vulnerability in Zimbra Collaboration Suite 8.8.15 allows attackers to inject malicious scripts via webmail calendar endpoints. When exploited, this can lead to session hijacking, credential theft, or redirection to malicious sites. Organizations running Zimbra 8.8.15 with webmail enabled are affected.
💻 Affected Systems
- Zimbra Collaboration Suite
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attacker steals administrator credentials, gains full control of Zimbra instance, accesses all organizational emails and data, and potentially pivots to internal networks.
Likely Case
Attacker steals user session cookies, impersonates legitimate users to read/send emails, and potentially accesses sensitive information in mailboxes.
If Mitigated
With proper web application firewalls and input validation, malicious payloads are blocked before reaching the vulnerable endpoint.
🎯 Exploit Status
Reflected XSS typically requires user interaction (clicking malicious link) but can be delivered via phishing or embedded in other sites.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 8.8.15 Patch 46 (P46)
Vendor Advisory: https://wiki.zimbra.com/wiki/Zimbra_Security_Advisories
Restart Required: Yes
Instructions:
1. Download Zimbra 8.8.15 Patch 46 from official sources. 2. Backup current installation. 3. Apply patch following Zimbra patch procedures. 4. Restart Zimbra services. 5. Verify patch application.
🔧 Temporary Workarounds
Web Application Firewall Rules
allConfigure WAF to block malicious script patterns targeting calendar endpoints
WAF-specific configuration commands vary by vendor
Input Validation Filter
linuxImplement custom input validation for calendar endpoint parameters
Modify Zimbra webmail configuration to sanitize calendar-related inputs
🧯 If You Can't Patch
- Restrict access to webmail interface using network segmentation or VPN
- Implement Content Security Policy headers to restrict script execution
🔍 How to Verify
Check if Vulnerable:
Test calendar endpoints with safe XSS payloads like <script>alert('test')</script> and check if reflected in responseCheck Version:
zmcontrol -vVerify Fix Applied:
After patching, retest with same payloads; scripts should be properly sanitized or blocked📡 Detection & Monitoring
Log Indicators:
- Unusual GET/POST requests to calendar endpoints with script tags
- Multiple failed login attempts following suspicious calendar requests
Network Indicators:
- HTTP requests containing script tags in URL parameters to /calendar/ endpoints
- Outbound connections to suspicious domains following calendar page visits
SIEM Query:
source="zimbra.log" AND (uri="*calendar*" AND (param="*<script>*" OR param="*javascript:*"))