Siemens SIMATIC MV500

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 9.8
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Siemens
• Equipment: SIMATIC MV500
• Vulnerabilities: Classic Buffer Overflow, NULL Pointer Dereference, Improper Authentication, Inefficient Regular Expression Complexity, Excessive Iteration, Out-of-bounds Write

2. RISK EVALUATION

Successful exploitation of these vulnerabilities could allow an attacker to achieve a denial-of-service condition, arbitrary code execution, or escalate privileges.

3.1 AFFECTED PRODUCTS

The following products of Siemens, are affected:

• SIMATIC MV500 family: Versions prior to V3.3.5

3.2 Vulnerability Overview

3.2.1 BUFFER COPY WITHOUT CHECKING SIZE OF INPUT ('CLASSIC BUFFER OVERFLOW') CWE-120

The deprecated compatibility function svcunix_create in the sunrpc module of the GNU C Library (aka glibc) through 2.34 copies its path argument on the stack without validating its length, which may result in a buffer overflow, potentially resulting in a denial of service or (if an application is not built with a stack protector enabled) arbitrary code execution.

CVE-2022-23218 has been assigned to this vulnerability. A CVSS v3 base score of 9.8 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

3.2.2 BUFFER COPY WITHOUT CHECKING SIZE OF INPUT ('CLASSIC BUFFER OVERFLOW') CWE-120

The deprecated compatibility function clnt_create in the sunrpc module of the GNU C Library (aka glibc) through 2.34 copies its hostname argument on the stack without validating its length, which may result in a buffer overflow, potentially resulting in a denial of service or (if an application is not built with a stack protector enabled) arbitrary code execution.

CVE-2022-23219 has been assigned to this vulnerability. A CVSS v3 base score of 9.8 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

3.2.3 NULL POINTER DEREFERENCE CWE-476

handle_ipDefaultTTL in agent/mibgroup/ip-mib/ip_scalars.c in Net-SNMP 5.8 through 5.9.3 has a NULL Pointer Exception bug that can be used by a remote attacker (who has write access) to cause the instance to crash via a crafted UDP packet, resulting in denial of service.

CVE-2022-44792 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H).

3.2.4 NULL POINTER DEREFERENCE CWE-476

handle_ipv6IpForwarding in agent/mibgroup/ip-mib/ip_scalars.c in Net-SNMP 5.4.3 through 5.9.3 has a NULL pointer exception bug that can be used by a remote attacker to cause the instance to crash via a crafted UDP packet, resulting in denial of service.

CVE-2022-44793 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H).

3.2.5 IMPROPER AUTHENTICATION CWE-287

The AES-SIV cipher implementation contains a bug that causes it to ignore empty associated data entries which are unauthenticated as a consequence. Impact summary: Applications that use the AES-SIV algorithm and want to authenticate empty data entries as associated data can be misled by removing adding or reordering such empty entries as these are ignored by the OpenSSL implementation. We are currently unaware of any such applications. The AES-SIV algorithm allows for authentication of multiple associated data entries along with the encryption. To authenticate empty data the application has to call EVP_EncryptUpdate() (or EVP_CipherUpdate()) with NULL pointer as the output buffer and 0 as the input buffer length. The AES-SIV implementation in OpenSSL just returns success for such a call instead of performing the associated data authentication operation. The empty data thus will not be authenticated. As this issue does not affect non-empty associated data authentication and we expect it to be rare for an application to use empty associated data entries this is qualified as Low severity issue.

CVE-2023-2975 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N).

3.2.6 INEFFICIENT REGULAR EXPRESSION COMPLEXITY CWE-1333

Checking excessively long DH keys or parameters may be very slow. Impact summary: Applications that use the functions DH_check(), DH_check_ex() or EVP_PKEY_param_check() to check a DH key or DH parameters may experience long delays. Where the key or parameters that are being checked have been obtained from an untrusted source this may lead to a Denial of Service. The function DH_check() performs various checks on DH parameters. One of those checks confirms that the modulus ('p' parameter) is not too large. Trying to use a very large modulus is slow and OpenSSL will not normally use a modulus which is over 10,000 bits in length. However, the DH_check() function checks numerous aspects of the key or parameters that have been supplied. Some of those checks use the supplied modulus value even if it has already been found to be too large. An application that calls DH_check() and supplies a key or parameters obtained from an untrusted source could be vulernable to a Denial-of-Service attack. The function DH_check() is itself called by a number of other OpenSSL functions. An application calling any of those other functions may similarly be affected. The other functions affected by this are DH_check_ex() and EVP_PKEY_param_check(). Also vulnerable are the OpenSSL dhparam and pkeyparam command line applications when using the '-check' option. The OpenSSL SSL/TLS implementation is not affected by this issue. The OpenSSL 3.0 and 3.1 FIPS providers are not affected by this issue.

CVE-2023-3446 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).

3.2.7 EXCESSIVE ITERATION CWE-834

Checking excessively long DH keys or parameters may be very slow. Impact summary: Applications that use the functions DH_check(), DH_check_ex() or EVP_PKEY_param_check() to check a DH key or DH parameters may experience long delays. Where the key or parameters that are being checked have been obtained from an untrusted source this may lead to a Denial of Service. The function DH_check() performs various checks on DH parameters. After fixing CVE-2023-3446 it was discovered that a large q parameter value can also trigger an overly long computation during some of these checks. A correct q value, if present, cannot be larger than the modulus p parameter, thus it is unnecessary to perform these checks if q is larger than p. An application that calls DH_check() and supplies a key or parameters obtained from an untrusted source could be vulnerable to a Denial-of-Service attack. The function DH_check() is itself called by a number of other OpenSSL functions. An application calling any of those other functions may similarly be affected. The other functions affected by this are DH_check_ex() and EVP_PKEY_param_check(). Also vulnerable are the OpenSSL dhparam and pkeyparam command line applications when using the "-check" option. The OpenSSL SSL/TLS implementation is not affected by this issue. The OpenSSL 3.0 and 3.1 FIPS providers are not affected by this issue.

CVE-2023-3817 has been assigned to this vulnerability. A CVSS v3 base score of 5.3 has been assigned; the CVSS vector string is (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L).

3.2.8 OUT-OF-BOUNDS WRITE CWE-787

An issue was discovered in fl_set_geneve_opt in net/sched/cls_flower.c in the Linux kernel before 6.3.7. It allows an out-of-bounds write in the flower classifier code via TCA_FLOWER_KEY_ENC_OPTS_GENEVE packets. This may result in denial of service or privilege escalation.

CVE-2023-35788 has been assigned to this vulnerability. A CVSS v3 base score of 7.8 has been assigned; the CVSS vector string is (CVSS:3.1/AV:L/AC:L/PR:L/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 these vulnerabilities to CISA.

4. MITIGATIONS

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

• SIMATIC MV500 family: Update to V3.3.5 or later version

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-099606 in HTML and CSAF.

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

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 exploitation specifically targeting these vulnerabilities has been reported to CISA at this time.

5. UPDATE HISTORY

• November 16, 2023: Initial Publication

• Siemens