CVE-2025-27457
📋 TL;DR
CVE-2025-27457 is a cleartext transmission vulnerability in VNC communications that allows attackers to intercept unencrypted traffic between VNC servers and clients. This exposes sensitive data like credentials, keystrokes, and screen contents to network eavesdropping. Any organization using vulnerable VNC implementations for remote access or management is affected.
💻 Affected Systems
- SICK VNC implementations
- Endress VNC implementations
- Other VNC software with similar configuration
📦 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
Complete compromise of all data transmitted via VNC including administrative credentials, sensitive documents, and full control sessions, leading to system takeover and lateral movement.
Likely Case
Credential theft and session hijacking allowing unauthorized access to systems and sensitive information exposure.
If Mitigated
Limited exposure of non-sensitive data with proper network segmentation and monitoring detecting interception attempts.
🎯 Exploit Status
Standard network sniffing tools can intercept VNC traffic. No authentication bypass needed as traffic is cleartext.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: N/A
Vendor Advisory: https://sick.com/psirt
Restart Required: No
Instructions:
1. Check vendor advisory for specific guidance. 2. Enable VNC encryption if supported. 3. Consider alternative secure remote access solutions.
🔧 Temporary Workarounds
Enable VNC Encryption
allConfigure VNC server to use encryption (TLS/SSL) for all connections
vncserver -SecurityTypes=TLSPlain,TLSNone
x11vnc -ssl /path/to/cert.pem
SSH Tunnel for VNC
allTunnel VNC traffic through encrypted SSH connection
ssh -L 5901:localhost:5901 user@vnc-server
vncviewer localhost:5901
🧯 If You Can't Patch
- Implement network segmentation to isolate VNC traffic from untrusted networks
- Use VPN for all remote VNC access to encrypt traffic at network layer
🔍 How to Verify
Check if Vulnerable:
Use network analyzer (Wireshark/tcpdump) on port 5900-5910 to check if VNC traffic is unencryptedCheck Version:
vncserver --version or check application documentationVerify Fix Applied:
Confirm encrypted traffic on VNC ports using network analyzer and verify TLS/SSL handshake📡 Detection & Monitoring
Log Indicators:
- Failed encryption handshakes
- Multiple connection attempts from unknown IPs
- Unusual VNC session patterns
Network Indicators:
- Cleartext VNC traffic on network
- Port scanning on 5900-5910
- Man-in-the-middle attack patterns
SIEM Query:
source_port=5900-5910 AND protocol="RFB" AND NOT tls_handshake🔗 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
