CVE-2021-31894:Write permission vulnerability in Siemens SIMATIC and SINAMICS products allows attackers to manipulate device configurations.

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Description Preview

A security vulnerability has been identified in multiple Siemens industrial automation products including SIMATIC PCS 7, SIMATIC PDM, SIMATIC STEP 7, and SINAMICS STARTER. The issue stems from incorrect write permissions on a directory containing metafiles that are relevant to device configurations. An attacker with access to the affected system could exploit this vulnerability by modifying the content of these metafiles, which would subsequently allow them to manipulate parameters or alter the behavior of devices that are later configured using the affected software. This could potentially lead to unauthorized configuration changes and compromise the integrity of industrial control systems.

Overview

The vulnerability affects multiple Siemens industrial automation products, specifically:

  • SIMATIC PCS 7 V8.2 and earlier (All versions)
  • SIMATIC PCS 7 V9.X (All versions < V9.1 SP2)
  • SIMATIC PDM (All versions < V9.2 SP2)
  • SIMATIC STEP 7 V5.X (All versions < V5.7)
  • SINAMICS STARTER (containing STEP 7 OEM version) (All versions < V5.4 SP2 HF1)

The core issue is that a directory containing configuration metafiles has incorrect write permissions, allowing unauthorized modification of these files. If exploited, an attacker could alter device parameters or change the behavior of industrial devices when they are configured using the affected software. This vulnerability could potentially impact the integrity and reliability of industrial control systems, leading to unexpected behavior or operational disruptions in industrial environments.

Remediation

To mitigate this vulnerability, Siemens recommends the following actions:

  1. Update to the latest software versions:

    • SIMATIC PCS 7: Update to V9.1 SP2 or later
    • SIMATIC PDM: Update to V9.2 SP2 or later
    • SIMATIC STEP 7 V5.X: Update to V5.7 or later
    • SINAMICS STARTER: Update to V5.4 SP2 HF1 or later

  2. If immediate updates are not possible:

    • Restrict access to the affected systems to trusted personnel only
    • Implement network segmentation to isolate the affected systems
    • Monitor for any unauthorized changes to configuration files
    • Follow defense-in-depth security practices for industrial control systems

  3. Review the Siemens Security Advisory SSA-661034 for detailed patching instructions and additional mitigation strategies.

References

  1. Siemens Security Advisory SSA-661034: https://cert-portal.siemens.com/productcert/pdf/ssa-661034.pdf
  2. MITRE CVE-2021-31894: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-31894
  3. Siemens ProductCERT: https://cert-portal.siemens.com/productcert/

Industry ExposureMost to least
This section illustrates the prevalence of a specific Common Vulnerabilities and Exposures (CVE) across various industries based on customer reports. The ranking displays industries from the most to least affected by this particular vulnerability, offering valuable insight into where this CVE has been most frequently observed. This information can help organizations within these sectors prioritize their security efforts, understand their relative risk exposure compared to their peers, and focus remediation strategies where they are most needed. By understanding the industry-specific impact, organizations can make more informed decisions regarding patching, resource allocation, and overall risk management related to this CVE.

  1. Manufacturing
    Manufacturing
  2. Health Care & Social Assistance
    Health Care & Social Assistance
  3. Professional, Scientific, & Technical Services
    Professional, Scientific, & Technical Services
  4. Accommodation & Food Services
    Accommodation & Food Services
  5. Administrative, Support, Waste Management & Remediation Services
    Administrative, Support, Waste Management & Remediation Services
  6. Agriculture, Forestry Fishing & Hunting
    Agriculture, Forestry Fishing & Hunting
  7. Arts, Entertainment & Recreation
    Arts, Entertainment & Recreation
  8. Construction
    Construction
  9. Educational Services
    Educational Services
  10. Finance and Insurance
    Finance and Insurance
  11. Information
    Information
  12. Management of Companies & Enterprises
    Management of Companies & Enterprises
  13. Mining
    Mining
  14. Other Services (except Public Administration)
    Other Services (except Public Administration)
  15. Public Administration
    Public Administration
  16. Real Estate Rental & Leasing
    Real Estate Rental & Leasing
  17. Retail Trade
    Retail Trade
  18. Transportation & Warehousing
    Transportation & Warehousing
  19. Utilities
    Utilities
  20. Wholesale Trade
    Wholesale Trade

Focus on What Matters

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  3. Proactively Mitigate Threats.

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