CVE-2023-51771
📋 TL;DR
This vulnerability in MicroHttpServer allows a one-byte buffer overflow via a long URI in the _ParseHeader function. Attackers can exploit this to potentially execute arbitrary code or crash the server. Anyone using MicroHttpServer versions through commit a8ab029 is affected.
💻 Affected Systems
- MicroHttpServer (aka Micro HTTP Server)
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise, data theft, or ransomware deployment.
Likely Case
Denial of service through server crashes, with potential for limited code execution depending on memory layout.
If Mitigated
Server crashes but no code execution due to modern exploit mitigations like ASLR and stack canaries.
🎯 Exploit Status
Simple buffer overflow with public details but no confirmed weaponization.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Versions after commit a8ab029
Vendor Advisory: https://github.com/starnight/MicroHttpServer/issues/8
Restart Required: Yes
Instructions:
1. Update to latest MicroHttpServer version. 2. Recompile if using source. 3. Restart the HTTP server service.
🔧 Temporary Workarounds
URI Length Limiting
allConfigure reverse proxy or load balancer to reject excessively long URIs before reaching MicroHttpServer.
nginx: 'client_max_body_size 1k;' in location block
apache: 'LimitRequestLine 1024' in config
Network Segmentation
linuxRestrict access to MicroHttpServer instances to trusted networks only.
iptables -A INPUT -p tcp --dport 80 -s trusted_network -j ACCEPT
iptables -A INPUT -p tcp --dport 80 -j DROP
🧯 If You Can't Patch
- Replace MicroHttpServer with alternative HTTP server software.
- Deploy WAF with buffer overflow protection rules.
🔍 How to Verify
Check if Vulnerable:
Check if MicroHttpServer version includes commit a8ab029 or earlier in git history.Check Version:
git log --oneline -1Verify Fix Applied:
Verify current version is newer than commit a8ab029 and test with long URI requests.📡 Detection & Monitoring
Log Indicators:
- HTTP requests with unusually long URIs (>1024 characters)
- Server crash/restart logs
Network Indicators:
- HTTP GET requests with URI length exceeding normal patterns
SIEM Query:
source="web_logs" AND uri_length>1024