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1. EXECUTIVE SUMMARY
- CVSS v3 7.5
- ATTENTION: Exploitable remotely/low skill level to exploit
- Vendor: Siemens
- Equipment: SCALANCE and SIMATIC
- Vulnerability: Out-of-bounds Read
2. UPDATE INFORMATION
This updated advisory is a follow-up to the original advisory titled ICSA-21-068-10 Siemens SCALANCE and SIMATIC libcurl that was published March 9, 2021, on the ICS webpage on us-cert.cisa.gov.
3. RISK EVALUATION
Successful exploitation of this third-party vulnerability could allow an attacker to cause a denial-of-service condition on the affected devices.
4. TECHNICAL DETAILS
4.1 AFFECTED PRODUCTS
The following Siemens products are affected by the third-party component libcurl:
- SCALANCE SC600 Family: all versions prior to v2.0
- SIMATIC NET CM 1542-1: all versions
--------- Begin Update A Part 1 of 1 ---------
- SIMATIC NET CP 343-1 Advanced (incl. SIPLUS variants): v3.0.33, v3.0.44 and v3.0.53
--------- End Update A Part 1 of 1 ---------
4.2 VULNERABILITY OVERVIEW
The libcurl library Versions 7.34.0 through 7.63.0 are vulnerable to a heap out-of-bounds read condition in the code handling the end-of-response for SMTP. This vulnerability could allow an attacker to trigger a denial-of-service condition on the affected devices.
- CRITICAL INFRASTRUCTURE SECTORS: Multiple
- COUNTRIES/AREAS DEPLOYED: Worldwide
- COMPANY HEADQUARTERS LOCATION: Germany
Siemens reported this vulnerability to CISA.
Siemens has identified the following specific workarounds and mitigations users can apply to reduce risk:
- SCALANCE SC600: Update to v2.0 or later
- Disable the SMTP Client function on affected devices or use VPN for protecting SMTP traffic to trusted email servers only.
The impact of additional libcurl vulnerabilities is described in Siemens Security Advisory SSA-436177
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 the 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 this vulnerability.
For any questions related to this report, please contact the CISA at:
Toll Free: 1-888-282-0870
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