CVE-2026-22781
📋 TL;DR
TinyWeb HTTP Server versions before 1.98 are vulnerable to unauthenticated remote command injection via CGI ISINDEX-style query parameters. Attackers can execute arbitrary OS commands on Windows servers by injecting shell metacharacters into HTTP requests. This affects all deployments using vulnerable versions with CGI functionality enabled.
💻 Affected Systems
- TinyWeb HTTP Server
📦 What is this software?
Tinyweb by Ritlabs
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise allowing attacker to install malware, exfiltrate data, pivot to internal networks, or deploy ransomware.
Likely Case
Web server compromise leading to data theft, website defacement, or use as attack platform for further exploitation.
If Mitigated
Limited impact if proper network segmentation, least privilege, and monitoring are in place.
🎯 Exploit Status
Simple HTTP request with shell metacharacters can trigger exploitation.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.98
Vendor Advisory: https://github.com/maximmasiutin/TinyWeb/security/advisories/GHSA-m779-84h5-72q2
Restart Required: Yes
Instructions:
1. Download TinyWeb 1.98 from official repository. 2. Stop TinyWeb service. 3. Replace executable with patched version. 4. Restart service.
🔧 Temporary Workarounds
Disable CGI functionality
windowsRemove or disable CGI execution capability in TinyWeb configuration.
Edit TinyWeb configuration to remove CGI directory mappings and disable ISINDEX support
Network isolation
windowsRestrict access to TinyWeb server using firewall rules.
netsh advfirewall firewall add rule name="Block TinyWeb CGI" dir=in action=block protocol=TCP localport=80,443 remoteip=any
🧯 If You Can't Patch
- Implement strict network segmentation to isolate TinyWeb server from critical systems
- Deploy web application firewall (WAF) with command injection detection rules
🔍 How to Verify
Check if Vulnerable:
Check TinyWeb version via HTTP headers or configuration file. If version < 1.98 and CGI enabled, system is vulnerable.Check Version:
Check TinyWeb.exe properties or HTTP Server header responseVerify Fix Applied:
Confirm version is 1.98 or higher and test CGI functionality with safe test parameters.📡 Detection & Monitoring
Log Indicators:
- HTTP requests containing shell metacharacters (&, |, ;, %) in query parameters
- Unusual process creation from TinyWeb CGI processes
Network Indicators:
- HTTP requests to CGI endpoints with suspicious parameters
- Outbound connections from web server to unexpected destinations
SIEM Query:
source="TinyWeb" AND (url="*cgi*" AND (query="*&*" OR query="*|*" OR query="*;*" OR query="*`*"))