CVE-2023-32320
📋 TL;DR
This vulnerability in Nextcloud Server allows attackers to bypass rate limiting protections by sending parallel requests, enabling brute-force attacks on protected details like passwords or tokens. It affects Nextcloud Server and Enterprise Server versions before the patched releases. Attackers can exploit this to compromise user accounts or sensitive data.
💻 Affected Systems
- Nextcloud Server
- Nextcloud Enterprise Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete account takeover through brute-force password attacks, unauthorized access to sensitive files, or administrative privilege escalation.
Likely Case
Successful brute-force attacks against user credentials, API tokens, or other protected details leading to data breaches.
If Mitigated
Limited impact with proper network segmentation, strong authentication, and monitoring, though rate limiting bypass remains possible.
🎯 Exploit Status
Exploitation requires sending parallel HTTP requests; tools like Burp Suite or custom scripts can automate this.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Nextcloud Server: 25.0.7, 26.0.2; Nextcloud Enterprise Server: 21.0.9.12, 22.2.10.12, 23.0.12.7, 24.0.12.2, 25.0.7, 26.0.2
Vendor Advisory: https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qphh-6xh7-vffg
Restart Required: No
Instructions:
1. Backup your Nextcloud instance. 2. Update to the patched version via the Nextcloud updater or manual installation. 3. Verify the update completed successfully.
🔧 Temporary Workarounds
Implement Web Application Firewall (WAF) Rate Limiting
linuxConfigure external WAF or reverse proxy to enforce strict rate limiting on Nextcloud endpoints.
# Example for nginx: limit_req_zone $binary_remote_addr zone=nextcloud:10m rate=10r/s;
# Add 'limit_req zone=nextcloud burst=20 nodelay;' to server block
Reduce Parallel Request Limits
allConfigure web server to limit concurrent connections per IP to mitigate parallel request attacks.
# Apache: LimitRequestBody, LimitRequestFields
# nginx: limit_conn_zone and limit_conn directives
🧯 If You Can't Patch
- Implement network-level rate limiting using firewalls or load balancers to restrict requests per IP.
- Enable multi-factor authentication (MFA) for all users to reduce impact of credential brute-forcing.
🔍 How to Verify
Check if Vulnerable:
Check Nextcloud version via Admin Panel > Overview or run: php occ statusCheck Version:
php occ status | grep 'versionstring'Verify Fix Applied:
Confirm version matches patched releases and test rate limiting with parallel request tools.📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts from single IP in short timeframe
- High volume of parallel requests to login or API endpoints
Network Indicators:
- Unusual spike in HTTP requests from single source
- Patterns of simultaneous requests bypassing normal rate limits
SIEM Query:
source="nextcloud.log" AND ("Login failed" OR "rate limit") | stats count by src_ip | where count > 100🔗 References
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qphh-6xh7-vffg
- https://github.com/nextcloud/server/pull/38274
- https://hackerone.com/reports/1918525
- https://github.com/nextcloud/security-advisories/security/advisories/GHSA-qphh-6xh7-vffg
- https://github.com/nextcloud/server/pull/38274
- https://hackerone.com/reports/1918525
