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Siemens SIMATIC UltraVNC HMI WinCC Products

Act Now9.8ICS-CERT ICSA-21-131-11May 11, 2021
Attack VectorNetwork
Auth RequiredNone
ComplexityLow
User InteractionNone needed
Summary

UltraVNC vulnerabilities in Siemens SIMATIC HMI panels and WinCC Runtime software allow remote code execution, information disclosure, and denial-of-service attacks via port 5900/TCP. The vulnerabilities stem from memory corruption issues (CWE-125, CWE-122, CWE-121, CWE-788) that can be triggered without authentication or user interaction. Affected versions include Comfort Outdoor Panels 7\" and 15\", Comfort Panels 4\" through 22\", KTP Mobile Panels (KTP400F, KTP700, KTP700F, KTP900, KTP900F), and WinCC Runtime Advanced versions prior to v16 Update 4.

What this means
What could happen
An attacker with network access to the VNC service (port 5900) could execute arbitrary code on Siemens HMI panels or WinCC Runtime, potentially altering operator displays, process setpoints, or halting plant operations.
Who's at risk
Manufacturing facilities using Siemens SIMATIC HMI panels (Comfort Outdoor Panels 7\" and 15\", Comfort Panels 4\" to 22\", KTP Mobile Panels) and WinCC Runtime Advanced software for process visualization and SCADA control. Any facility relying on these panels for operator control and monitoring of manufacturing processes is affected if running firmware versions prior to v16 Update 4.
How it could be exploited
An attacker sends a crafted packet to port 5900/TCP on an exposed HMI panel or WinCC Runtime. No credentials or user interaction is required. The vulnerability in UltraVNC allows memory corruption that leads to remote code execution on the device running the HMI or SCADA software.
Prerequisites
  • Network access to port 5900/TCP on the HMI device or WinCC Runtime system
  • Device must be running affected firmware versions (prior to v16 Update 4)
remotely exploitableno authentication requiredlow complexityhigh CVSS score (9.8)affects HMI/SCADA visualization and controlpartial patch availability (WinCC only)
Exploitability
Moderate exploit probability (EPSS 5.4%)
Affected products (4)
1 with fix3 pending
ProductAffected VersionsFix Status
SIMATIC HMI Comfort Outdoor Panels 7" & 15" (incl. SIPLUS variants)<V16 Update 4No fix yet
SIMATIC HMI Comfort Panels 4" - 22" (incl. SIPLUS variants)<V16 Update 4No fix yet
SIMATIC HMI KTP Mobile Panels KTP400F, KTP700, KTP700F, KTP900 and KTP900F<V16 Update 4No fix yet
SIMATIC WinCC Runtime Advanced<V16 Update 416 Update 4
Remediation & Mitigation
0/7
Do now
0/2
WORKAROUNDRestrict access to port 5900/TCP to only trusted IP addresses using firewall rules
HARDENINGIsolate HMI and WinCC systems from the internet and untrusted networks
Schedule — requires maintenance window
0/4

Patching may require device reboot — plan for process interruption

SIMATIC WinCC Runtime Advanced
HOTFIXUpdate SIMATIC WinCC Runtime Advanced to v16 Update 4 or later
All products
HOTFIXUpdate SIMATIC HMI Comfort Outdoor Panels 7" and 15" to v16 Update 4 or later
HOTFIXUpdate SIMATIC HMI Comfort Panels 4" - 22" to v16 Update 4 or later
HOTFIXUpdate SIMATIC HMI KTP Mobile Panels (KTP400F, KTP700, KTP700F, KTP900, KTP900F) to v16 Update 4 or later
Long-term hardening
0/1
HARDENINGPlace control system networks behind firewalls and separate from business networks
View full CISA ICS-CERT advisory
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Siemens SIMATIC UltraVNC HMI WinCC Products | CVSS 9.8 - OTPulse