CVE-2025-66902
📋 TL;DR
An input validation vulnerability in Pithikos websocket-server v0.6.4 allows remote attackers to trigger unexpected server behavior or potentially leak sensitive information through malformed WebSocket messages. This affects any application using the vulnerable websocket-server library version. Attackers can exploit this without authentication to cause denial of service or information disclosure.
💻 Affected Systems
- Pithikos websocket-server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete server crash leading to denial of service, potential memory corruption allowing remote code execution, or sensitive information leakage including server memory contents.
Likely Case
Server instability, unexpected behavior, or denial of service through malformed WebSocket messages, potentially exposing error messages or partial data.
If Mitigated
Limited impact with proper input validation at application layer, though server may still experience performance degradation.
🎯 Exploit Status
Public proof-of-concept available on GitHub demonstrates exploitation. Attack requires only network access to WebSocket endpoint.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not available
Vendor Advisory: Not available
Restart Required: Yes
Instructions:
1. Check if using websocket-server v0.6.4. 2. Consider upgrading to a maintained fork or alternative library. 3. Implement input validation in application code. 4. Restart affected services after changes.
🔧 Temporary Workarounds
Input Validation Wrapper
allImplement custom input validation before passing messages to WebSocketServer._message_received
# Python code to validate WebSocket messages
# Add validation logic before calling _message_received method
Network Segmentation
allRestrict WebSocket server access to trusted networks only
# Firewall rule example (Linux)
iptables -A INPUT -p tcp --dport [WEBSOCKET_PORT] -s [TRUSTED_NETWORK] -j ACCEPT
# Firewall rule example (Windows)
New-NetFirewallRule -DisplayName "WebSocket Restrict" -Direction Inbound -LocalPort [WEBSOCKET_PORT] -RemoteAddress [TRUSTED_NETWORK] -Action Allow
🧯 If You Can't Patch
- Implement Web Application Firewall (WAF) rules to filter malformed WebSocket traffic
- Monitor server logs for unusual WebSocket message patterns and implement rate limiting
🔍 How to Verify
Check if Vulnerable:
Check Python dependencies: pip show websocket-server | grep VersionCheck Version:
pip show websocket-server | grep VersionVerify Fix Applied:
Test with proof-of-concept from GitHub repository to confirm server no longer exhibits unexpected behavior📡 Detection & Monitoring
Log Indicators:
- Unusual WebSocket connection errors
- Server crashes or restarts
- Memory error messages in logs
- Malformed WebSocket frame warnings
Network Indicators:
- Abnormal WebSocket traffic patterns
- Rapid connection attempts to WebSocket endpoints
- Unusually large or malformed WebSocket messages
SIEM Query:
source="websocket.log" AND (error OR crash OR "malformed" OR "invalid")