CVE-2025-27458
📋 TL;DR
This vulnerability in VNC authentication allows attackers to capture challenge-response pairs from unencrypted network traffic and attempt to derive the password through offline brute-force attacks. It affects any system using VNC with the vulnerable authentication mechanism. Industrial control systems and remote access implementations are particularly at risk.
💻 Affected Systems
- VNC implementations using challenge-response authentication
📦 What is this software?
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise leading to unauthorized access, data theft, and potential lateral movement within networks.
Likely Case
Unauthorized access to VNC sessions allowing screen viewing, keyboard/mouse control, and credential harvesting.
If Mitigated
Limited impact if strong passwords are used and network segmentation prevents traffic interception.
🎯 Exploit Status
Attack requires network access to capture authentication traffic but uses well-understood cryptographic weaknesses.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: https://sick.com/psirt
Restart Required: No
Instructions:
No official patch available. Implement workarounds and consider alternative remote access solutions.
🔧 Temporary Workarounds
Enable VNC encryption
allConfigure VNC to use TLS/SSL encryption for all traffic
vncserver -SecurityTypes=TLSPlain,TLSNone,X509Plain,X509None
Use SSH tunneling
allTunnel VNC traffic through SSH for encryption
ssh -L 5901:localhost:5901 user@vnc-server
🧯 If You Can't Patch
- Implement network segmentation to isolate VNC traffic from untrusted networks
- Use strong, complex passwords and enforce regular password rotation
🔍 How to Verify
Check if Vulnerable:
Check if VNC is running without encryption: netstat -an | grep 5900-5910 and verify traffic is not encryptedCheck Version:
vncserver --version or check VNC client/server documentationVerify Fix Applied:
Verify VNC traffic is encrypted using Wireshark or similar tools to confirm TLS/SSL is active📡 Detection & Monitoring
Log Indicators:
- Multiple failed authentication attempts
- Unusual source IP addresses connecting to VNC port
Network Indicators:
- Unencrypted VNC traffic on port 5900+
- Challenge-response patterns in network captures
SIEM Query:
source_port:5900-5910 AND protocol:TCP AND NOT (tls OR ssl)🔗 References
- https://sick.com/psirt
- https://sick.com/psirt
- https://www.cisa.gov/resources-tools/resources/ics-recommended-practices
- https://www.endress.com
- https://www.first.org/cvss/calculator/3.1
- https://www.sick.com/.well-known/csaf/white/2025/sca-2025-0008.json
- https://www.sick.com/.well-known/csaf/white/2025/sca-2025-0008.pdf
