CVE-2021-33591
📋 TL;DR
This vulnerability allows remote attackers to execute arbitrary code on systems running vulnerable versions of Naver Comic Viewer. Attackers can exploit an exposed remote debugging port via a crafted HTML page. Users of Naver Comic Viewer prior to version 1.0.15.0 are affected.
💻 Affected Systems
- Naver Comic Viewer
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the victim's computer, enabling data theft, ransomware deployment, or persistent backdoor installation.
Likely Case
Remote code execution leading to malware installation, credential theft, or system disruption for users who visit malicious websites while the viewer is running.
If Mitigated
No impact if the vulnerable software is not installed or has been updated to the patched version.
🎯 Exploit Status
Exploitation requires the victim to visit a malicious HTML page while the vulnerable software is running.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 1.0.15.0
Vendor Advisory: https://cve.naver.com/detail/cve-2021-33591
Restart Required: Yes
Instructions:
1. Download Naver Comic Viewer version 1.0.15.0 or later from the official Naver website. 2. Uninstall the previous version. 3. Install the updated version. 4. Restart the system.
🔧 Temporary Workarounds
Disable Naver Comic Viewer
windowsUninstall or disable the vulnerable software until patching is possible.
Control Panel > Programs > Uninstall a program > Select Naver Comic Viewer > Uninstall
Network Blocking
windowsBlock outbound connections from Naver Comic Viewer using firewall rules.
New-NetFirewallRule -DisplayName "Block Naver Comic Viewer" -Direction Outbound -Program "C:\Program Files\Naver\ComicViewer\*.exe" -Action Block
🧯 If You Can't Patch
- Implement application whitelisting to prevent unauthorized executables from running.
- Use network segmentation to isolate systems running the vulnerable software.
🔍 How to Verify
Check if Vulnerable:
Check the installed version of Naver Comic Viewer via Control Panel > Programs > Programs and Features.Check Version:
wmic product where name="Naver Comic Viewer" get versionVerify Fix Applied:
Verify the installed version is 1.0.15.0 or higher and that the remote debugging port is no longer exposed.📡 Detection & Monitoring
Log Indicators:
- Unusual process creation from Naver Comic Viewer executable
- Network connections to unusual ports from the viewer process
Network Indicators:
- Outbound connections from Naver Comic Viewer to suspicious IP addresses
- Traffic on unexpected ports from the viewer
SIEM Query:
Process Creation: (ImagePath contains "Naver Comic Viewer") AND (CommandLine contains unusual parameters)