Siemens SCALANCE W1750D Devices

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).

1. EXECUTIVE SUMMARY

• CVSS v3 7.4
• ATTENTION: Exploitable remotely  
• Vendor: Siemens  
• Equipment: SCALANCE W1750D 
• Vulnerabilities: Inadequate Encryption Strength, Double Free, Use After Free, Improper Input Validation 

2. RISK EVALUATION

Successful exploitation of these vulnerabilities could allow an attacker to read memory contents, decrypt RSA-encrypted messages, or create a denial-of-service condition. 

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following software from Siemens is affected: 

• SCALANCE W1750D (JP) (6GK5750-2HX01-1AD0): All versions  
• SCALANCE W1750D (ROW) (6GK5750-2HX01-1AA0): All versions 
• SCALANCE W1750D (USA) (6GK5750-2HX01-1AB0): All versions  

3.2 VULNERABILITY OVERVIEW

3.2.1 INADEQUATE ENCRYPTION STRENGTH CWE-326 

A timing-based side channel exists in the OpenSSL RSA Decryption implementation which could be sufficient to recover a plaintext across a network in a Bleichenbacher style attack. The vulnerability affects all RSA padding modes: PKCS#1 v1.5, RSA-OEAP, and RSASVE. After a sufficiently large number of messages, the attacker could recover the pre-master secret used for the original connection and thus decrypt the application data sent over that connection. 

CVE-2022-4304 has been assigned to this vulnerability. A CVSS v3 base score of 5.9 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N). 

3.2.2 DOUBLE FREE CWE-415 

It is possible to construct a PEM file that results in 0 bytes of payload data. In this case, PEM_read_bio_ex() will return a failure code but will populate the header argument with a pointer to a buffer that has already been freed. If the caller also frees this buffer then a double free will occur. This will most likely lead to a crash. This could be exploited by an attacker who can supply malicious PEM files for parsing to achieve a denial-of-service condition. 

CVE-2022-4450 has been assigned to this vulnerability. A CVSS v3 base score of 5.9 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H). 

3.2.3 USE AFTER FREE CWE-416 

Under certain conditions, if a CMS recipient public key is invalid, the new filter BIO is freed and the function returns a NULL result indicating a failure. However, in this case, the BIO chain is not properly cleaned up and the BIO passed by the caller still retains internal pointers to the previously freed filter BIO. If the caller then goes on to call BIO_pop() on the BIO, a use after free will occur. This will most likely result in a crash. 

CVE-2023-0215 has been assigned to this vulnerability. A CVSS v3 base score of 5.9 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H). 

3.2.4 IMPROPER INPUT VALIDATION CWE-20 

A type confusion vulnerability could allow an attacker to pass arbitrary pointers to a memcmp call, enabling them to read memory contents or enact a denial-of-service condition. 

CVE-2023-0286 has been assigned to this vulnerability. A CVSS v3 base score of 7.4 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H). 

3.3 BACKGROUND

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

3.4 RESEARCHER

Siemens reported these vulnerabilities to CISA. 

4. MITIGATIONS

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

• CVE-2023-0286: Disable CRL (certification revocation list) checking, if possible. 
• CVE-2022-4450: Do not import or configure certificate files in PEM format from untrusted sources. 
• CVE-2022-4304: Disable the use of RSA ciphers in the web server configuration; note that RSA ciphers are disabled by default. 

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. Additional information on Siemens Industrial Security can be found here. 

For more information, see the associated Siemens security advisory SSA-203374 in HTML and CSAF. 

CISA recommends users take defensive measures to minimize the risk of exploitation of these vulnerabilities. Specifically, users should:

• Minimize network exposure for all control system devices and/or systems, and ensure they are not accessible from the Internet.
• Locate control system networks and remote devices behind firewalls and isolate them from business networks.
• 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 its 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 at cisa.gov/ics. 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.

Additional mitigation guidance and recommended practices are publicly available on the ICS webpage at cisa.gov/ics 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.

CISA also recommends users take the following measures to protect themselves from social engineering attacks: 

• Do not click web links or open attachments in unsolicited email messages. 
• Refer to Recognizing and Avoiding Email Scams for more information on avoiding email scams. 
• Refer to Avoiding Social Engineering and Phishing Attacks for more information on social engineering attacks. 

No known public exploits specifically target these vulnerabilities. These vulnerabilities have a high attack complexity.