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1. EXECUTIVE SUMMARY
- CVSS v3 8.1
- ATTENTION: Exploitable remotely/low attack complexity
- Vendor: Siemens
- Equipment: Nucleus NET, Nucleus RTOS, Nucleus Source Code, VSTAR
- Vulnerabilities: Out-of-bounds Write, Use of Out-of-Range Pointer Offset
2. RISK EVALUATION
Successful exploitation of these vulnerabilities could allow a denial-of-service condition or for the execution of code remotely.
3. TECHNICAL DETAILS
3.1 AFFECTED PRODUCTS
The following Nucleus products are affected:
- Nucleus NET: All versions prior to v5.2
- Nucleus RTOS: Versions including affected DNS modules
- Nucleus Source Code: Versions including affected DNS modules
- VSTAR: Versions including affected DNS modules
3.2 VULNERABILITY OVERVIEW
The DNS domain name label parsing functionality does not properly validate the names in DNS-responses. The parsing of malformed responses could result in a write past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to execute code in the context of the current process or cause a denial-of-service condition.
The DNS domain name record decompression functionality does not properly validate the pointer offset values. The parsing of malformed responses could result in a write past the end of an allocated structure. An attacker with a privileged position in the network could leverage this vulnerability to execute code in the context of the current process or cause a denial-of-service condition.
- CRITICAL INFRASTRUCTURE SECTORS: Multiple Sectors
- COUNTRIES/AREAS DEPLOYED: Worldwide
- COMPANY HEADQUARTERS LOCATION: Germany
Daniel dos Santos, from Forescout Technologies, and Siemens reported these vulnerabilities to CISA.
Siemens has published security advisory SSA-185699 and released the following mitigations for the affected products:
- Nucleus NET: Follow general security measures or upgrade to the latest versions of Nucleus ReadyStart or Nucleus 4. Note the latest version of Nucleus NET (v5.2) is not affected by the vulnerabilities but is already beyond end of software support.
- Nucleus RTOS: Contact customer support to receive patch and update information.
- Nucleus Source Code: Contact customer support to receive patch and update information.
- VSTAR: Contact customer support to receive patch and update information.
Siemens has identified the following specific workarounds and mitigations users can apply to reduce risk:
- Avoid using DNS client of affected versions.
- For additional mitigation advice contact Siemens customer support or a Nucleus Sales team.
As a general security measure, Siemens strongly recommends protecting network access to devices with appropriate mechanisms. In order to operate the devices in a protected IT environment, Siemens recommends to configure the environment according to Siemens’ Operational Guidelines for Industrial Security, and to follow the recommendations in the product manuals.
Additional information on industrial security by Siemens can be found at: https://www.siemens.com/industrialsecurity
For further inquiries on security vulnerabilities in Siemens’ products and solutions, contact Siemens ProductCERT.
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.
For any questions related to this report, please contact the CISA at:
Toll Free: 1-888-282-0870
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