Siemens SCALANCE and SIMATIC libcurl

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. RISK EVALUATION

Successful exploitation of this third-party vulnerability could allow an attacker to cause a denial-of-service condition on the affected devices.

3. TECHNICAL DETAILS

3.1 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

3.2 VULNERABILITY OVERVIEW

3.2.1 OUT-OF-BOUNDS READ CWE-125

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.

CVE-2019-3823 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been assigned; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

3.3 BACKGROUND

• **CRITICAL INFRASTRUCTURE SECTORS:**Multiple
• **COUNTRIES/AREAS DEPLOYED:**Worldwide
• COMPANY HEADQUARTERS LOCATION: Germany

3.4 RESEARCHER

Siemens reported this vulnerability to CISA.

4. MITIGATIONS

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.

Contact Information

For any questions related to this report, please contact the CISA at:

Email: [email protected]
Toll Free: 1-888-282-0870

For industrial control systems cybersecurity information: https://us-cert.cisa.gov/ics
or incident reporting: https://us-cert.cisa.gov/report

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