CVE-2023-28356
📋 TL;DR
This vulnerability allows attackers to send specially crafted messages containing specific character chains that cause a chat service process to enter an infinite loop, consuming excessive CPU resources (~120%) and making the service unresponsive. It affects chat services that process user messages without proper input validation.
💻 Affected Systems
- Chat services with vulnerable message processing
📦 What is this software?
Rocket.chat by Rocket.chat
⚠️ Risk & Real-World Impact
Worst Case
Complete service outage and denial of service affecting all users, potentially leading to extended downtime and business disruption.
Likely Case
Targeted denial of service against specific chat instances or channels, causing temporary unavailability for affected users.
If Mitigated
Limited impact with proper rate limiting, input validation, and monitoring in place to detect and block malicious messages quickly.
🎯 Exploit Status
Exploitation requires sending a malicious message with specific character chains, which is relatively simple to craft and execute.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor advisory for specific patched versions
Vendor Advisory: https://hackerone.com/reports/1461340
Restart Required: Yes
Instructions:
1. Check vendor advisory for patched version. 2. Update to patched version. 3. Restart chat service. 4. Verify fix is applied.
🔧 Temporary Workarounds
Input Validation Filter
allImplement input validation to reject messages containing suspicious character sequences or patterns
Implementation depends on specific chat platform - add input validation in message processing logic
Rate Limiting
allImplement rate limiting on message sending to prevent rapid exploitation attempts
Configure rate limiting in chat service settings or web application firewall
🧯 If You Can't Patch
- Implement web application firewall (WAF) rules to block messages containing suspicious character patterns
- Monitor CPU usage on chat processes and implement automated alerts for abnormal spikes
🔍 How to Verify
Check if Vulnerable:
Check if chat service processes messages without proper input validation for character sequencesCheck Version:
Check chat service version using appropriate command for your platformVerify Fix Applied:
Test sending messages with various character patterns and monitor CPU usage remains normal📡 Detection & Monitoring
Log Indicators:
- Unusually high CPU usage logs
- Process restart logs
- Messages with unusual character patterns in chat logs
Network Indicators:
- Multiple rapid message submissions
- Messages containing specific character patterns
SIEM Query:
source="chat_logs" AND (message="*specific_pattern*" OR cpu_usage>90)