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 9.1
ATTENTION: Exploitable remotely/low attack complexity
Vendor: Siemens
Equipment: SIDIS Prime
Vulnerabilities: Use of Insufficiently Random Values, NULL Pointer Dereference, Infinite Loop

2. RISK EVALUATION

Successful exploitation of these vulnerabilities could allow an unauthenticated attacker with access to the network where SIDIS Prime is installed to reuse OPC UA client credentials, create a denial-of-service condition of the SIDIS Prime OPC UA client, or create a denial-of-service condition of the SIDIS Prime TLS service.

3. TECHNICAL DETAILS

3.1 AFFECTED PRODUCTS

The following Siemens products are affected:

SIDIS Prime: All versions prior to V4.0.400

3.2 Vulnerability Overview

3.2.1 USE OF INSUFFICIENTLY RANDOM VALUES CWE-330

In OPC Foundation OPC UA .NET Standard codebase 1.4.357.28, servers do not create sufficiently random numbers in OPCFoundation.NetStandard.Opc.Ua before 1.4.359.31, which allows man-in-the-middle attackers to reuse encrypted user credentials sent over the network.

CVE-2019-19135 has been assigned to this vulnerability. A CVSS v3 base score of 7.4 has been calculated; the CVSS vector string is (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N).

A CVSS v4 score has also been calculated for CVE-2019-19135. A base score of 9.1 has been calculated; the CVSS vector string is (CVSS4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N.

3.2.2 NULL POINTER DEREFERENCE CWE-476

Server or client applications that call the SSL_check_chain() function during or after a TLS 1.3 handshake may crash due to a NULL pointer dereference as a result of incorrect handling of the “signature_algorithms_cert” TLS extension. The crash occurs if an invalid or unrecognized signature algorithm is received from the peer. This could be exploited by a malicious peer in a denial-of-service attack.

CVE-2020-1967 has been assigned to this vulnerability. A CVSS v3 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:N/I:N/A:H).

A CVSS v4 score has also been calculated for CVE-2020-1967. A base score of 8.7 has been calculated; the CVSS vector string is (CVSS4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N.

3.2.3 NULL POINTER DEREFERENCE CWE-476

The X.509 GeneralName type is a generic type for representing different types of names. One of those name types is known as EDIPartyName. OpenSSL provides a function GENERAL_NAME_cmp which compares different instances of a GENERAL_NAME to see if they are equal or not. This function behaves incorrectly when both GENERAL_NAMEs contain an EDIPARTYNAME. A NULL pointer dereference and a crash may occur leading to a possible denial-of-service attack. OpenSSL itself uses the GENERAL_NAME_cmp function for two purposes: 1) Comparing CRL distribution point names between an available CRL and a CRL distribution point embedded in an X509 certificate. 2) When verifying that a timestamp response token signer matches the timestamp authority name (exposed via the API functions TS_RESP_verify_response and TS_RESP_verify_token). If an attacker can control both items being compared, then that attacker could trigger a crash. For example, if the attacker can trick a client or server into checking a malicious certificate against a malicious CRL, then this may occur. Note that some applications automatically download CRLs based on a URL embedded in a certificate. This checking happens prior to the signatures on the certificate and CRL being verified. OpenSSL’s s_server, s_client and verify tools have support for the “-crl_download” option which implements automatic CRL downloading and this attack has been demonstrated to work against those tools. Note that an unrelated bug means that affected versions of OpenSSL cannot parse or construct correct encodings of EDIPARTYNAME. However, it is possible to construct a malformed EDIPARTYNAME that OpenSSL’s parser will accept and hence trigger this attack.

CVE-2020-1971 has been assigned to this vulnerability. A CVSS v3 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:N/I:N/A:H).

A CVSS v4 score has also been calculated for CVE-2020-1971. A base score of 8.2 has been calculated; the CVSS vector string is (CVSS4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N.

3.2.4 LOOP WITH UNREACHABLE EXIT CONDITION (‘INFINITE LOOP’) CWE-835

The BN_mod_sqrt() function in openSSL, which computes a modular square root, contains a bug that can cause it to loop forever for non-prime moduli. Internally this function is used when parsing certificates that contain elliptic curve public keys in compressed form or explicit elliptic curve parameters with a base point encoded in compressed form. It is possible to trigger an infinite loop by crafting a certificate that has invalid explicit curve parameters. Since certificate parsing happens prior to verification of the certificate signature, any process that parses an externally supplied certificate may thus be subject to a denial-of-service attack. The infinite loop can also be reached when parsing crafted private keys as they can contain explicit elliptic curve parameters.

CVE-2022-0778 has been assigned to this vulnerability. A CVSS v3 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:N/I:N/A:H).

A CVSS v4 score has also been calculated for CVE-2022-0778. A base score of 8.7 has been calculated; the CVSS vector string is (CVSS4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N.

3.2.5 LOOP WITH UNREACHABLE EXIT CONDITION (‘INFINITE LOOP’) CWE-835

An infinite loop in OPC UA .NET Standard Stack 1.04.368 allows a remote attackers to cause the application to hang via a crafted message.

CVE-2022-29862 has been assigned to this vulnerability. A CVSS v3 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:N/I:N/A:H).

A CVSS v4 score has also been calculated for CVE-2022-29862. A base score of 8.7 has been calculated; the CVSS vector string is (CVSS4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N.

3.3 BACKGROUND

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

3.4 RESEARCHER

Siemens reported these vulnerabilities to CISA.

4. MITIGATIONS

Siemens has released a new version of SIDIS Prime and recommends users update to the latest version:

Update to V4.0.400 or later version

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

Enable encrypted communication between the affected product (OPC UA client) and the OPC UA server(s)

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-108696 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

February 15, 2024: Initial Publication