Siemens NX OBJ Translator

1. EXECUTIVE SUMMARY

• CVSS v3 7.8 *ATTENTION: low attack complexity
• Vendor: Siemens
• Equipment: NX
• Vulnerabilities: Use After Free, Access of Uninitialized Pointer

2. RISK EVALUATION

Successful exploitation of these vulnerabilities could lead to an access violation and arbitrary code execution on the target system.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

Siemens reports these vulnerabilities affects the following NX products:

• NX 1953 Series: All versions prior to v1973.3700
• NX 1980 Series: All versions prior to v1988

3.2 VULNERABILITY OVERVIEW

3.2.1 USE AFTER FREE CWE-416

The affected application contains a use-after-free vulnerability while parsing OBJ files. An attacker could leverage this vulnerability to execute code in the context of the current process.

CVE-2021-41535 has been assigned to this vulnerability. A CVSS v3 base score of 7.8 has been calculated; the CVSS vector string is (AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H).

3.2.2 ACCESS OF UNINITIALIZED POINTER CWE-824

The affected application is vulnerable to information disclosure by unexpected access to an uninitialized pointer while parsing user-supplied OBJ files. An attacker could leverage this vulnerability to leak information from memory locations.

CVE-2021-41538 has been assigned to this vulnerability. A CVSS v3 base score of 3.3 has been calculated; the CVSS vector string is (AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N).

3.3 BACKGROUND

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

3.4 RESEARCHER

xina1i working, with Trend Micro’s Zero Day Initiative, reported these vulnerabilities to Siemens and CISA.

4. MITIGATIONS

Siemens has released updates for the NX and recommends updating to the latest version.

• NX 1953 Series: Update to v1973.3700 or later version
• NX 1980 Series: Update to v1988 or later version

Siemens recommends users avoid opening of untrusted files from unknown sources.

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

For more information about this issue, please see Siemens security advisory SSA-328042

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

• Do not click web links or open unsolicited attachments in 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.

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 these vulnerabilities. These vulnerabilities are not exploitable remotely.