CVE-2025-63651
📋 TL;DR
A use-after-free vulnerability in Monkey web server's string handling function allows attackers to crash the server by sending specially crafted HTTP requests. This affects all Monkey web server deployments running vulnerable versions, potentially causing service disruption.
💻 Affected Systems
- Monkey web server
📦 What is this software?
Monkey by Monkey Project
⚠️ Risk & Real-World Impact
Worst Case
Complete denial of service with server crash and potential memory corruption that could lead to remote code execution in specific conditions.
Likely Case
Server crash and service disruption requiring restart, with possible memory leak or instability.
If Mitigated
Limited impact with proper network segmentation and monitoring, though service interruption may still occur.
🎯 Exploit Status
Exploitation requires sending crafted HTTP requests but no authentication. No public proof-of-concept has been identified.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Commit f37e984 and later
Vendor Advisory: https://github.com/archersec/security-advisories/blob/master/monkey/monkey-advisory-2025.md
Restart Required: Yes
Instructions:
1. Update Monkey web server to commit f37e984 or later. 2. Rebuild from source if using source installation. 3. Restart the Monkey service. 4. Verify the fix is applied.
🔧 Temporary Workarounds
Network filtering
allImplement web application firewall rules to block suspicious HTTP requests
Rate limiting
allConfigure request rate limiting to reduce impact of potential DoS attempts
🧯 If You Can't Patch
- Implement network segmentation to isolate Monkey servers from untrusted networks
- Deploy monitoring and alerting for server crashes or abnormal HTTP request patterns
🔍 How to Verify
Check if Vulnerable:
Check Monkey version or commit hash against vulnerable versions prior to f37e984Check Version:
monkey --version or check build/commit informationVerify Fix Applied:
Verify current commit hash includes f37e984 or later, and test with normal HTTP traffic📡 Detection & Monitoring
Log Indicators:
- Server crash logs
- Abnormal termination messages
- Memory error logs in system logs
Network Indicators:
- Unusual HTTP request patterns
- Multiple connection attempts with malformed requests
SIEM Query:
source="monkey.log" AND ("crash" OR "segmentation fault" OR "use-after-free")