Siemens SIRIUS 3SK2 Safety Relays and 3RK3 Modular Safety Systems

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 v4 8.7
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Siemens
• Equipment: SIRIUS 3RK3 Modular Safety System (MSS), SIRIUS Safety Relays 3SK2
• Vulnerabilities: Use of a Broken or Risky Cryptographic Algorithm, Missing Encryption of Sensitive Data, Incorrect Permission Assignment for Critical Resource

2. RISK EVALUATION

Successful exploitation of these vulnerabilities could allow an attacker to retrieve and de-obfuscate safety password, eavesdrop connections, or retrieve sensitive information from certain data records.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

Siemens reports that the following products are affected:

• SIRIUS 3RK3 Modular Safety System (MSS): All versions
• SIRIUS Safety Relays 3SK2: All versions

3.2 VULNERABILITY OVERVIEW

3.2.1 USE OF A BROKEN OR RISKY CRYPTOGRAPHIC ALGORITHM CWE-327

Affected devices only provide weak password obfuscation. An attacker with network access could retrieve and de-obfuscate the safety password used for protection against inadvertent operating errors.

CVE-2025-24007 has been assigned to this vulnerability. A CVSS v3.1 base score of 7.5 has been calculated; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).

A CVSS v4 score has also been calculated for CVE-2025-24007. A base score of 8.7 has been calculated; the CVSS vector string is (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N).

3.2.2 MISSING ENCRYPTION OF SENSITIVE DATA CWE-311

The affected devices do not encrypt data in transit. An attacker with network access could eavesdrop the connection and retrieve sensitive information, including obfuscated safety passwords.

CVE-2025-24008 has been assigned to this vulnerability. A CVSS v3.1 base score of 6.5 has been calculated; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:N).

A CVSS v4 score has also been calculated for CVE-2025-24008. A base score of 8.7 has been calculated; the CVSS vector string is (CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N).

3.2.3 INCORRECT PERMISSION ASSIGNMENT FOR CRITICAL RESOURCE CWE-732

The affected devices do not require authentication to access critical resources. An attacker with network access could retrieve sensitive information from certain data records, including obfuscated safety passwords.

CVE-2025-24009 has been assigned to this vulnerability. A CVSS v3.1 base score of 5.9 has been calculated; the CVSS vector string is (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N).

A CVSS v4 score has also been calculated for CVE-2025-24009. A base score of 8.2 has been calculated; the CVSS vector string is (CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N).

3.3 BACKGROUND

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

3.4 RESEARCHER

Nikolai Puch, Johanna Latzel, and Ferdinand Jarisch from Fraunhofer AISEC reported these vulnerabilities to Siemens.

4. MITIGATIONS

Siemens is preparing fixed versions and recommends countermeasures for products where fixes are not, or not yet available:

• SIRIUS 3RK3 Modular Safety System (MSS): Currently no fix is planned.
• SIRIUS Safety Relays 3SK2: Currently no fix is available.

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

• Limit physical access to affected devices to trusted personnel.
• Ensure network isolation of the PROFINET interface to prevent access from unauthorized systems.

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-222768 in HTML and CSAF.

CISA recommends users take defensive measures to minimize the risk of exploitation of these vulnerabilities. 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 these vulnerabilities has been reported to CISA at this time.

5. UPDATE HISTORY

• May 15, 2025: Initial Republication of Siemens ProductCERT SSA-222768

• Siemens