CVE-2020-13768
📋 TL;DR
CVE-2020-13768 is a critical stack-based buffer overflow vulnerability in MiniShare HTTP server that allows unauthenticated remote attackers to execute arbitrary code via specially crafted HTTP PUT requests. This affects all MiniShare versions before 1.4.2. The product is discontinued, leaving users with no official vendor support.
💻 Affected Systems
- MiniShare HTTP Server
📦 What is this software?
Minishare by Minishare 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 allowing attackers to gain control of the server, pivot to internal networks, and deploy malware.
If Mitigated
Limited impact if server is isolated with strict network controls, though buffer overflow could still cause denial of service.
🎯 Exploit Status
Public exploit code available on GitHub. Similar to previous CVEs in same product (CVE-2018-19861, CVE-2018-19862, CVE-2019-17601).
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.4.2 (but product discontinued)
Vendor Advisory: None - product discontinued
Restart Required: Yes
Instructions:
1. Upgrade to version 1.4.2 if available 2. Restart MiniShare service 3. Verify PUT method is disabled
🔧 Temporary Workarounds
Disable HTTP PUT Method
allDisable PUT method in MiniShare configuration to prevent exploitation
Edit MiniShare configuration file to remove or comment PUT method support
Network Segmentation
allRestrict network access to MiniShare server
firewall-cmd --permanent --remove-service=http --zone=public
netsh advfirewall firewall add rule name="Block MiniShare" dir=in action=block protocol=TCP localport=80,443
🧯 If You Can't Patch
- Immediately remove MiniShare from production environments
- Replace with maintained HTTP server software (Apache, Nginx, IIS)
🔍 How to Verify
Check if Vulnerable:
Check MiniShare version: if version < 1.4.2, system is vulnerable. Test with HTTP PUT request to see if server responds.Check Version:
Check MiniShare interface or configuration file for version informationVerify Fix Applied:
Verify version is 1.4.2 or higher. Test that HTTP PUT requests are rejected or disabled.📡 Detection & Monitoring
Log Indicators:
- Unusual HTTP PUT requests
- Large payloads in PUT requests
- Stack overflow errors in system logs
Network Indicators:
- HTTP PUT requests with oversized headers or data
- Multiple failed PUT attempts
- Shellcode patterns in HTTP traffic
SIEM Query:
source="minishare.log" AND (method="PUT" AND (bytes>10000 OR contains(data,"\x90\x90")))