CVE-2020-18698
📋 TL;DR
This vulnerability allows remote attackers to perform unlimited brute force login attempts against Lin-CMS-Flask without any rate limiting or account lockout mechanisms. Attackers can guess user credentials through automated attacks, potentially gaining unauthorized access to the CMS. All systems running the vulnerable version are affected.
💻 Affected Systems
- Lin-CMS-Flask
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the CMS with administrative access, leading to data theft, website defacement, or further network penetration.
Likely Case
Successful credential guessing leading to unauthorized user access, potentially escalating to administrative privileges.
If Mitigated
Failed login attempts logged but no successful compromise due to strong passwords and monitoring.
🎯 Exploit Status
Simple HTTP POST requests to login endpoint with different credentials.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: v0.1.2 or later
Vendor Advisory: https://github.com/TaleLin/lin-cms-flask/issues/27
Restart Required: Yes
Instructions:
1. Backup current installation. 2. Update to v0.1.2 or later via pip: 'pip install --upgrade lin-cms-flask'. 3. Restart the Flask application.
🔧 Temporary Workarounds
Web Application Firewall (WAF) Rules
allImplement rate limiting on /api/cms/user/login endpoint
Reverse Proxy Rate Limiting
linuxConfigure nginx or Apache to limit login attempts
nginx: limit_req_zone $binary_remote_addr zone=login:10m rate=5r/m;
nginx: limit_req zone=login burst=10 nodelay;
🧯 If You Can't Patch
- Implement network-level restrictions to limit access to login endpoint
- Enable detailed logging and monitoring for brute force patterns
🔍 How to Verify
Check if Vulnerable:
Check if login endpoint at /api/cms/user/login accepts unlimited rapid requests without rate limiting.Check Version:
pip show lin-cms-flask | grep VersionVerify Fix Applied:
Test that login endpoint now implements rate limiting or account lockout after multiple failed attempts.📡 Detection & Monitoring
Log Indicators:
- Multiple failed login attempts from same IP
- Rapid succession of POST requests to login endpoint
Network Indicators:
- High volume of HTTP 401/403 responses from login endpoint
- Pattern of credential guessing traffic
SIEM Query:
source="web_logs" AND uri_path="/api/cms/user/login" AND (status=401 OR status=403) | stats count by src_ip | where count > 10