Siemens Industrial Products

As of January 10, 2023, CISA will no longer be updating ICS security advisories for Siemens product vulnerabilities beyond the initial advisory. For the most up-to-date information on vulnerabilities in this advisory, please see Siemens' ProductCERT Security Advisories (CERT Services | Services | Siemens Global). 

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1. EXECUTIVE SUMMARY

• CVSS v3 8.1
• ATTENTION: Exploitable remotely
• Vendor: Siemens
• Equipment: Industrial Edge Management OS (IEM-OS), SINEMA Remote Connect Server, SINUMERIK ONE
• Vulnerability: Signal Handler Race Condition

2. RISK EVALUATION

Successful exploitation of this vulnerability could allow an unauthenticated remote attacker to achieve remote code execution with high impact on the affected system.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following Siemens products are affected:

• Industrial Edge Management OS (IEM-OS): All versions
• SINEMA Remote Connect Server: All versions prior to V3.2 SP2
• SINUMERIK ONE: All versions prior to V6.24

3.2 Vulnerability Overview

3.2.1 SIGNAL HANDLER RACE CONDITION CWE-364

A security regression (CVE-2006-5051) was discovered in OpenSSH's server (sshd). There is a race condition which can lead to sshd to handle some signals in an unsafe manner. An unauthenticated, remote attacker may be able to trigger it by failing to authenticate within a set time period.

CVE-2024-6387 has been assigned to this vulnerability. A CVSS v3 base score of 8.1 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).

3.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Critical Manufacturing
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: Germany

3.4 RESEARCHER

Siemens reported this vulnerability to CISA.

4. MITIGATIONS

Siemens recommends users apply the following updates:

• SINEMA Remote Connect Server: Update to V3.2 SP2 or later version.

For SINUMERIK ONE:

• This vulnerability can be triggered on all SINUMERIK interfaces (X120, X127, X130) if the ssh port is open to get root access.
• Updated software version can be obtained from Siemens customer support or a local partner.

Siemens has identified the following specific workarounds and mitigations that users can apply to reduce the risk:

• Disable SSH when possible
• Limit remote access to the SSH port (default: 22/tcp) to trusted systems only
• Change the default SSH port (22/tcp) to a nonstandard port to minimize success of automated attacks

As a general security measure, Siemens recommends protecting network access to devices with appropriate mechanisms. To operate the devices in a protected IT environment, Siemens recommends configuring the environment according to Siemens' operational guidelines for industrial security and following recommendations in the product manuals.

Additional information on industrial security by Siemens can be found on the Siemens industrial security webpage

For more information see the associated Siemens security advisory SSA-446545 in HTML and CSAF.

CISA recommends users take defensive measures to minimize the risk of exploitation of this vulnerability, such as:

• Minimize network exposure for all control system devices and/or systems, ensuring they are not accessible from the internet.
• Locate control system networks and remote devices behind firewalls and isolating them from business networks.
• When remote access is required, use more secure methods, such as virtual private networks (VPNs). Recognize VPNs may have vulnerabilities, should be updated to the most recent version available, and are 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 cisa.gov. Several CISA products detailing cyber defense best practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies.

CISA encourages organizations to implement recommended cybersecurity strategies for proactive defense of ICS assets.

Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov in the technical information paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies.

Organizations observing suspected malicious activity should follow established internal procedures and report findings to CISA for tracking and correlation against other incidents.

No known public exploitation specifically targeting this vulnerability has been reported to CISA at this time. This vulnerability has a high attack complexity.

5. UPDATE HISTORY

• September 12, 2024: Initial Publication

• Siemens