CVE-2023-4491
📋 TL;DR
A buffer overflow vulnerability in Easy Address Book Web Server 1.6 allows remote attackers to execute arbitrary code by sending an overly long username string via POST request to /searchbook.ghp. This affects all users running the vulnerable version of the software.
💻 Affected Systems
- Easy Address Book Web Server
📦 What is this software?
Easy Address Book Web Server by Easy Address Book Web Server Project
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with remote code execution leading to data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Remote code execution leading to web server compromise, data exfiltration, and lateral movement within the network.
If Mitigated
Attack blocked at network perimeter or detected before successful exploitation.
🎯 Exploit Status
The vulnerability requires no authentication and exploitation appears straightforward based on the description.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Unknown
Vendor Advisory: https://www.incibe.es/en/incibe-cert/notices/aviso/multiple-vulnerabilities-efs-software-products
Restart Required: Yes
Instructions:
1. Check vendor advisory for patch availability. 2. If patch exists, download and install. 3. Restart the web server service. 4. Verify the fix is applied.
🔧 Temporary Workarounds
Network Segmentation
allIsolate the vulnerable server from internet access and restrict internal network access.
Web Application Firewall
allDeploy WAF rules to block requests with excessive username length to /searchbook.ghp endpoint.
🧯 If You Can't Patch
- Immediately take the vulnerable server offline and replace with alternative software.
- Implement strict network access controls to limit exposure to only necessary users.
🔍 How to Verify
Check if Vulnerable:
Check the software version in the application interface or installation directory. If version is 1.6, the system is vulnerable.Check Version:
Check the application's about dialog or installation properties.Verify Fix Applied:
Verify the software version has been updated to a patched version (if available) or that the server is no longer accessible.📡 Detection & Monitoring
Log Indicators:
- Unusually long username strings in web server logs
- Multiple failed POST requests to /searchbook.ghp
- Crash or restart of the web server process
Network Indicators:
- POST requests to /searchbook.ghp with payloads exceeding normal username length
- Unusual outbound connections from the web server
SIEM Query:
source="web_server" AND (uri="/searchbook.ghp" AND request_length>1000) OR (process="easyserver.exe" AND event="crash")