CVE-2019-16536
📋 TL;DR
A stack overflow vulnerability in ClickHouse allows authenticated malicious clients to trigger denial of service by sending specially crafted requests. This affects ClickHouse database servers running versions before 19.14.3.3. Organizations using vulnerable ClickHouse instances with authenticated client access are at risk.
💻 Affected Systems
- ClickHouse
📦 What is this software?
Clickhouse by Clickhouse
⚠️ Risk & Real-World Impact
Worst Case
Complete service disruption of ClickHouse database, potentially affecting dependent applications and causing extended downtime.
Likely Case
Targeted DoS attacks against ClickHouse instances by authenticated malicious actors, causing temporary service unavailability.
If Mitigated
Limited impact with proper network segmentation, authentication controls, and monitoring in place.
🎯 Exploit Status
Exploitation requires authenticated access but is technically straightforward once authentication is obtained.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 19.14.3.3 and later
Vendor Advisory: https://clickhouse.com/docs/whats-new/security-changelog
Restart Required: Yes
Instructions:
1. Backup ClickHouse data and configuration. 2. Stop ClickHouse service. 3. Upgrade to version 19.14.3.3 or later using your package manager. 4. Restart ClickHouse service. 5. Verify successful upgrade and service functionality.
🔧 Temporary Workarounds
Restrict Client Access
linuxLimit network access to ClickHouse to only trusted IP addresses and required applications.
# Configure firewall rules to restrict access
iptables -A INPUT -p tcp --dport 9000 -s trusted_ip -j ACCEPT
iptables -A INPUT -p tcp --dport 9000 -j DROP
Enforce Strong Authentication
allImplement strong authentication mechanisms and limit user privileges to minimum required.
# Review and harden ClickHouse users.xml configuration
# Remove unnecessary users and restrict permissions
🧯 If You Can't Patch
- Implement strict network segmentation to isolate ClickHouse from untrusted networks
- Enforce least privilege access controls and monitor for suspicious authentication attempts
🔍 How to Verify
Check if Vulnerable:
Check ClickHouse version: SELECT version(); If version is earlier than 19.14.3.3, system is vulnerable.Check Version:
SELECT version();Verify Fix Applied:
After patching, verify version is 19.14.3.3 or later: SELECT version();📡 Detection & Monitoring
Log Indicators:
- Multiple authentication failures followed by service crashes
- Unusual client connections from unexpected sources
- ClickHouse service restart logs indicating crashes
Network Indicators:
- Unusual traffic patterns to ClickHouse port (default 9000)
- Multiple connection attempts from single source
SIEM Query:
source="clickhouse.log" AND ("segmentation fault" OR "stack overflow" OR "service crashed")