CVE-2024-37316
📋 TL;DR
Authenticated users in Nextcloud Calendar can create events with manipulated attachment data that causes bad redirects for participants when clicked. This affects all Nextcloud instances running vulnerable versions of the Calendar app. The vulnerability requires authenticated access to exploit.
💻 Affected Systems
- Nextcloud Calendar
📦 What is this software?
Calendar by Nextcloud
⚠️ Risk & Real-World Impact
Worst Case
Participants could be redirected to malicious websites, potentially leading to phishing attacks or credential theft.
Likely Case
Participants experience unexpected redirects to unintended or broken URLs when clicking calendar event attachments.
If Mitigated
With proper access controls limiting user permissions, the impact is reduced to authenticated users redirecting themselves or colleagues to benign but unexpected URLs.
🎯 Exploit Status
Exploitation requires authenticated user access. The vulnerability involves manipulating attachment data in calendar events.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.6.8 or 4.7.2
Vendor Advisory: https://github.com/nextcloud/security-advisories/security/advisories/GHSA-2r7q-vfmv-79qf
Restart Required: No
Instructions:
1. Access Nextcloud admin interface. 2. Navigate to Apps section. 3. Find Calendar app. 4. Update to version 4.6.8 or 4.7.2. 5. Verify update completes successfully.
🔧 Temporary Workarounds
Disable Calendar App
linuxTemporarily disable the Calendar app to prevent exploitation
occ app:disable calendar
Restrict User Permissions
allLimit which users can create calendar events with attachments
🧯 If You Can't Patch
- Implement strict access controls to limit which users can create calendar events
- Monitor calendar event creation logs for suspicious activity
🔍 How to Verify
Check if Vulnerable:
Check Calendar app version in Nextcloud admin interface or via occ command: occ app:list | grep calendarCheck Version:
occ app:list | grep calendarVerify Fix Applied:
Confirm Calendar app version is 4.6.8 or 4.7.2 or higher📡 Detection & Monitoring
Log Indicators:
- Unusual calendar event creation patterns
- Multiple redirect errors in web server logs
Network Indicators:
- Unexpected redirects from calendar attachment URLs
SIEM Query:
source="nextcloud.log" AND ("calendar" AND "attachment" AND "redirect")🔗 References
- https://github.com/nextcloud/calendar/pull/5966
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-2r7q-vfmv-79qf
- https://hackerone.com/reports/2457588
- https://github.com/nextcloud/calendar/pull/5966
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-2r7q-vfmv-79qf
- https://hackerone.com/reports/2457588
