CVE-2021-37909
📋 TL;DR
This vulnerability in the TSSServiSign component allows remote attackers to write arbitrary data to the Windows registry without proper permissions due to insufficient input validation. It can lead to hijacking attacks and execution of arbitrary code, affecting systems running vulnerable versions of the software. Attackers can exploit this to gain control over affected systems.
💻 Affected Systems
- TSSServiSign component
📦 What is this software?
Tssservisignadapter by Tssservisignadapter Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to full system compromise, data theft, or ransomware deployment.
Likely Case
Privilege escalation or unauthorized registry modifications enabling persistence or further attacks.
If Mitigated
Limited impact if systems are patched, isolated, or have strict access controls preventing exploitation.
🎯 Exploit Status
Exploitation is straightforward due to lack of input validation, but no public proof-of-concept was found in references.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Not specified in references; check vendor for updated version.
Vendor Advisory: https://www.twcert.org.tw/tw/cp-132-5093-76f04-1.html
Restart Required: Yes
Instructions:
1. Identify affected TSSServiSign component version. 2. Apply vendor-provided patch or update to latest version. 3. Restart system to ensure changes take effect.
🔧 Temporary Workarounds
Disable TSSServiSign component
windowsTemporarily disable the vulnerable component to prevent exploitation.
sc stop TSSServiSign
sc config TSSServiSign start= disabled
Restrict network access
windowsBlock inbound network traffic to the component using firewall rules.
netsh advfirewall firewall add rule name="Block TSSServiSign" dir=in action=block program="C:\Path\To\TSSServiSign.exe" enable=yes
🧯 If You Can't Patch
- Implement strict network segmentation to isolate affected systems from untrusted networks.
- Apply principle of least privilege to registry access and monitor for unauthorized changes.
🔍 How to Verify
Check if Vulnerable:
Check if TSSServiSign component is installed and running; review version against vendor advisories.Check Version:
wmic product where name="TSSServiSign" get versionVerify Fix Applied:
Verify patch installation via version check and ensure registry write attempts are logged or blocked.📡 Detection & Monitoring
Log Indicators:
- Unusual registry write events from TSSServiSign process
- Failed or unauthorized access attempts in Windows Event Logs
Network Indicators:
- Suspicious inbound connections to TSSServiSign service ports
- Anomalous network traffic patterns
SIEM Query:
EventID=4657 OR EventID=4663 AND ProcessName="TSSServiSign.exe"