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1. EXECUTIVE SUMMARY
- CVSS v3 9.8
- ATTENTION: Exploitable remotely
- Vendor: Siemens
- Equipment: SINAMICS Medium Voltage Products, Remote Access
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- Vulnerabilities: Improper Restriction of Operations Within the Bounds of a Memory Buffer, Access of Memory Location After End of Buffer, Uncontrolled Resource Consumption, Improper Initialization, Out-of-Bound Read, Heap-based Buffer Overflow, Stack-based Buffer Overflow, Improper Null Termination
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2. UPDATE INFORMATION
This updated advisory is a follow-up to the advisory update titled ICSA-21-131-04 Siemens Medium Voltage Products (Update A) that was published May 11, 2021, to the ICS webpage on us-cert.cisa.gov.
3. RISK EVALUATION
Successful exploitation of this vulnerability could allow an attacker to gain full remote access to the HMI.
4. TECHNICAL DETAILS
4.1 AFFECTED PRODUCTS
Siemens reports this vulnerability affects the following SINAMICS products with remote access enabled on SIMATIC comfort HMI Panels:
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- SINAMICS GH150: All versions
- SINAMICS GL150 (with option X30): All versions
- SINAMICS GM150 (with option X30): All versions
- SINAMICS SH150: All versions
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- SINAMICS SL150: All versions
- SINAMICS SM120: All versions
- SINAMICS SM150: All versions
- SINAMICS SM150i: All versions
4.2 VULNERABILITY OVERVIEW
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SmartVNC has a heap allocation leak vulnerability in the server Tight encoder, which could result in a denial-of-service condition.
SmartVNC has an out-of-bounds memory access vulnerability in the device layout handler, represented by a binary data stream on client side, which could result in code execution.
A remote attacker could send specially crafted packets to SmartVNC device layout handler on client side, which could influence the amount of resources consumed and result in a denial-of-service (infinite loop) condition.
SmartVNC has a heap allocation leak vulnerability in the device layout handler on client side, which could result in a denial-of-service condition.
UltraVNC Revision 1198 contains multiple memory leaks in VNC client code, which could allow an attacker to read stack memory and can be abused for information disclosure. Combined with another vulnerability, it can be used to leak stack memory and bypass ASLR.
UltraVNC Revision 1199 has an out-of-bounds read vulnerability in VNC client RRE decoder code, caused by multiplication overflow.
UltraVNC Revision 1199 has an out-of-bounds read vulnerability in VNC code inside client CoRRE decoder, caused by multiplication overflow.
UltraVNC Revision 1203 has multiple heap buffer overflow vulnerabilities in VNC client code inside Ultra decoder, which could result in code execution.
UltraVNC Revision 1205 has a stack-based buffer overflow vulnerability in VNC client code inside ShowConnInfo routine, which could lead to a denial-of-service condition.
UltraVNC Revision 1203 has an out-of-bounds access vulnerability in VNC client inside Ultra2 decoder, which could result in code execution.
UltraVNC Revision 1207 has multiple out-of-bounds access vulnerabilities connected with improper usage of SETPIXELS macro in VNC client code, which could result in code execution.
UltraVNC Revision 1211 has multiple improper null termination vulnerabilities in VNC server code, which could result in out-of-bounds data being accessed by remote users.
UltraVNC Revision 1211 contains multiple memory leaks in VNC server code, which could allow an attacker to read stack memory and can be abused for information disclosure.
UltraVNC Revision 1203 has out-of-bounds access vulnerability in VNC client inside RAW decoder, which could result in code execution.
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- CRITICAL INFRASTRUCTURE SECTORS: Chemical, Commercial Facilities, Critical Manufacturing, Energy, Food and Agriculture, Healthcare and Public Health, Transportation Systems, Water and Wastewater Systems
- COUNTRIES/AREAS DEPLOYED: Worldwide
- COMPANY HEADQUARTERS LOCATION: Germany
Siemens reported this vulnerability to CISA.
Only HMI image versions prior to v16 Update 3a are affected. Siemens recommends updating the following products to v16 Update 4 or later:
- SINAMICS GH150
- SINAMICS GL150 (with option X30)
- SINAMICS GM150 (with option X30)
- SINAMICS SH150
- SINAMICS SM120
Siemens has identified the following specific workarounds and mitigations users can apply to reduce the risk:
- Restrict access to Port 5900/TCP to trusted IP addresses only
- Disable Sm@rtServer in the SIMATIC HMI Comfort Panels system component of SINAMICS. If this is not possible, Defense-in-Depth should be used. Note: Sm@rtServer is disabled by default.
- Follow SINAMICS MV industrial security guidelines
As a general security measure, Siemens strongly recommends users protect network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends users configure the environment according to Siemens’ operational guidelines for industrial security, and follow the recommendations in the product manuals. Additional information on industrial security by Siemens can be found at: https://www.siemens.com/industrialsecurity
For additional information see Siemens Security Advisory SSA-286838
CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability. Specifically, users should:
- Minimize network exposure for all control system devices and/or systems, and ensure that they are not accessible from the Internet.
- Locate control system networks and remote devices behind firewalls, and isolate them from the business network.
- When remote access is required, use secure methods, such as Virtual Private Networks (VPNs), recognizing VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize VPN is only as secure as its connected devices.
CISA reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.
CISA also provides a section for control systems security recommended practices on the ICS webpage on us-cert.cisa.gov. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.
Additional mitigation guidance and recommended practices are publicly available on the ICS webpage on us-cert.cisa.gov in the Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.
Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to CISA for tracking and correlation against other incidents.
No known public exploits specifically target these vulnerabilities. These vulnerabilities have a high attack complexity.
For any questions related to this report, please contact the CISA at:
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