CVE-2025-40743
📋 TL;DR
This vulnerability allows attackers to bypass authentication on Siemens SINUMERIK CNC systems' VNC access service due to insufficient password verification. Affected systems include multiple SINUMERIK 828D, 840D sl, MC, and ONE models running vulnerable firmware versions. Successful exploitation could lead to unauthorized remote access to industrial control systems.
💻 Affected Systems
- SINUMERIK 828D PPU.4
- SINUMERIK 828D PPU.5
- SINUMERIK 840D sl
- SINUMERIK MC
- SINUMERIK MC V1.15
- SINUMERIK ONE
- SINUMERIK ONE V6.15
⚠️ 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 CNC system allowing unauthorized control of industrial machinery, potential physical damage, production disruption, and theft of proprietary manufacturing data.
Likely Case
Unauthorized access to CNC system interface allowing monitoring of operations, configuration changes, and potential disruption of manufacturing processes.
If Mitigated
Limited impact if systems are air-gapped, have network segmentation, or VNC service is disabled.
🎯 Exploit Status
Authentication bypass vulnerabilities typically require minimal technical skill to exploit once details are known. No public exploit code identified at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Update to: 828D PPU.4 V4.95 SP5, 828D PPU.5 V5.25 SP1, 840D sl V4.95 SP5, MC V1.25 SP1, MC V1.15 V1.15 SP5, ONE V6.25 SP1, ONE V6.15 V6.15 SP5
Vendor Advisory: https://cert-portal.siemens.com/productcert/html/ssa-177847.html
Restart Required: Yes
Instructions:
1. Download appropriate firmware update from Siemens support portal
2. Backup current configuration and programs
3. Apply firmware update following Siemens documentation
4. Restart system
5. Verify update was successful
🔧 Temporary Workarounds
Disable VNC Service
sinumerikDisable the vulnerable VNC access service if remote access is not required.
Configure via SINUMERIK HMI: System > Service > VNC > Disable
Network Segmentation
allIsolate SINUMERIK systems from untrusted networks using firewalls.
Configure firewall rules to block VNC port (typically 5900/tcp) from unauthorized networks
🧯 If You Can't Patch
- Implement strict network access controls to limit VNC service access to authorized IP addresses only.
- Monitor VNC authentication logs for unauthorized access attempts and implement alerting.
🔍 How to Verify
Check if Vulnerable:
Check firmware version via SINUMERIK HMI: System > Version > Display version information and compare against patched versions.Check Version:
On SINUMERIK HMI: Navigate to System > Version > Display version informationVerify Fix Applied:
Verify firmware version shows patched version and test VNC authentication requires proper credentials.📡 Detection & Monitoring
Log Indicators:
- Failed VNC authentication attempts followed by successful access
- VNC connections from unexpected IP addresses
- Multiple rapid VNC connection attempts
Network Indicators:
- VNC protocol traffic (port 5900/tcp) from unauthorized sources
- Unencrypted VNC authentication attempts
SIEM Query:
source="sinumerik_logs" AND (event="vnc_auth" AND result="success") AND NOT src_ip IN [authorized_ips]