CVE-2023-32319
📋 TL;DR
This vulnerability allows attackers to brute-force user credentials on Nextcloud servers via WebDAV endpoints when basic authentication is used and the username is not an email address. It affects Nextcloud server versions 24.0.0 and later. Successful exploitation could lead to unauthorized access to user accounts and sensitive data.
💻 Affected Systems
- Nextcloud Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Attackers gain administrative access to the Nextcloud instance, compromising all user data, installing malicious apps, or using the server as a pivot point for further network attacks.
Likely Case
Attackers compromise regular user accounts to access sensitive files, personal information, and potentially use those accounts for phishing or lateral movement.
If Mitigated
With proper patching and monitoring, the risk is limited to failed login attempts that can be detected and blocked before successful compromise.
🎯 Exploit Status
Exploitation requires only standard HTTP tools and knowledge of valid usernames. The vulnerability is in authentication logic, making automated attacks straightforward.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 24.0.11, 25.0.5, 26.0.0
Vendor Advisory: https://github.com/nextcloud/security-advisories/security/advisories/GHSA-mr7q-xf62-fw54
Restart Required: No
Instructions:
1. Backup your Nextcloud instance and database. 2. Update Nextcloud using the updater app or manually via command line. 3. For manual update: Download the patched version, extract, copy files to your Nextcloud directory, run occ upgrade. 4. Verify the update completed successfully.
🔧 Temporary Workarounds
No official workarounds
allThe vendor states there are no known workarounds for this vulnerability.
🧯 If You Can't Patch
- Implement network-level rate limiting for WebDAV endpoints (port 80/443) using firewalls or WAFs
- Monitor authentication logs for brute-force patterns and implement account lockouts
🔍 How to Verify
Check if Vulnerable:
Check your Nextcloud version via the admin interface or run: php occ status | grep versionCheck Version:
php occ status | grep versionVerify Fix Applied:
Verify version is 24.0.11+, 25.0.5+, or 26.0.0+ and check that WebDAV authentication logs show proper rate limiting📡 Detection & Monitoring
Log Indicators:
- Multiple failed WebDAV authentication attempts from single IP
- Successful WebDAV logins after many failures
- Unusual WebDAV activity patterns
Network Indicators:
- High volume of HTTP POST/OPTIONS requests to /remote.php/dav/ endpoints
- Traffic patterns suggesting credential stuffing
SIEM Query:
source="nextcloud.log" AND ("WebDAV authentication" OR "/remote.php/dav/") AND ("failed" OR "authenticated") | stats count by src_ip, user