CVE-2019-5476
📋 TL;DR
CVE-2019-5476 is an unauthenticated SQL injection vulnerability in Nextcloud Lookup-Server versions before 0.3.0. This allows attackers to execute arbitrary SQL commands on the lookup.nextcloud.com service, potentially compromising the entire database. All users running vulnerable versions of Nextcloud Lookup-Server are affected.
💻 Affected Systems
- Nextcloud Lookup-Server
📦 What is this software?
Lookup Server by Nextcloud
⚠️ Risk & Real-World Impact
Worst Case
Complete database compromise including data exfiltration, data manipulation, privilege escalation, and potential remote code execution via database functions.
Likely Case
Data theft from the lookup service database, potentially exposing user metadata and system information.
If Mitigated
Limited impact with proper input validation and database permissions, though SQL injection attempts would still be logged.
🎯 Exploit Status
SQL injection vulnerabilities are commonly exploited and this one requires no authentication, making it particularly dangerous.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v0.3.0 and later
Vendor Advisory: https://nextcloud.com/security/advisory/?id=NC-SA-2019-011
Restart Required: Yes
Instructions:
1. Update Nextcloud Lookup-Server to version 0.3.0 or later. 2. Restart the Lookup-Server service. 3. Verify the update was successful.
🔧 Temporary Workarounds
Network Isolation
linuxRestrict access to the Lookup-Server to trusted networks only
iptables -A INPUT -p tcp --dport 443 -s TRUSTED_NETWORK -j ACCEPT
iptables -A INPUT -p tcp --dport 443 -j DROP
🧯 If You Can't Patch
- Implement a Web Application Firewall (WAF) with SQL injection detection rules
- Disable the Lookup-Server service entirely if not required
🔍 How to Verify
Check if Vulnerable:
Check the Lookup-Server version. If it's below 0.3.0, it's vulnerable.Check Version:
Check the Lookup-Server configuration or deployment manifest for version informationVerify Fix Applied:
Confirm the Lookup-Server is running version 0.3.0 or higher and test SQL injection attempts are blocked.📡 Detection & Monitoring
Log Indicators:
- Unusual SQL queries in database logs
- Multiple failed login attempts from single IP
- SQL syntax errors in application logs
Network Indicators:
- HTTP requests containing SQL keywords (SELECT, UNION, etc.)
- Unusual traffic patterns to lookup endpoints
SIEM Query:
source="web_logs" AND ("SELECT" OR "UNION" OR "FROM" OR "WHERE") AND status="200"