Siemens SCALANCE W1750D (Update B)

1. EXECUTIVE SUMMARY

• CVSS v3 9.8
• ATTENTION: Exploitable remotely/low attack complexity
• Vendor: Siemens
• Equipment: SCALANCE W1750D
• Vulnerabilities: Improper Authentication, Classic Buffer Overflow, Command Injection, Improper Input Validation, Race Condition, Cross-site Scripting, Basic XSS, Uncontrolled Resource Consumption

2. UPDATE INFORMATION

This updated advisory is a follow-up to the original advisory titled ICSA-21-131-14 Siemens SCALANCE W1750D (Update A) that was published August 10, 2021, to the ICS webpage on us-cert.cisa.gov.

3. RISK EVALUATION

Successful exploitation of these vulnerabilities could allow an attacker to execute arbitrary code as a privileged user on the underlying operating system, fully compromise the underlying operating system, overwrite sensitive system files, create a denial-of-service condition, execute arbitrary script code in a victim’s browser, read arbitrary files off the underlying file system, create an attacker named directory, corrupt backup files, or obtain sensitive information.

4. TECHNICAL DETAILS

4.1 AFFECTED PRODUCTS

The following versions of SCALANCE W1750D, a software management platform, are affected:

• SCALANCE W1750D: All versions prior to 8.7.0

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• SCALANCE W1750D: v8.7.0 and later and prior to v8.7.1.3 (Only affected by CVE-2020-24635, CVE-2020-24636, CVE-2021-25145, CVE-2021-25146, CVE-2021-25155, CVE-2021-25156, CVE-2021-25157, CVE-2021-25158, CVE-2021-25159, CVE-2021-25160, CVE-2021-25161, and CVE-2021-25162).

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4.2 VULNERABILITY OVERVIEW

4.2.1    IMPROPER AUTHENTICATION CWE-287

An attacker with physical access to the affected device can bypass authentication mechanisms, which may allow access to the Aruba Instant command line interface.

CVE-2019-5317 has been assigned to this vulnerability. A CVSS v3 base score of 6.8 has been calculated; the CVSS vector string is (AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

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

An attacker may send specially crafted packets that may allow the execution of arbitrary code as a privileged user on the underlying operating system.

CVE-2019-5319 has been assigned to this vulnerability. A CVSS v3 base score of 9.8 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

4.2.3    IMPROPER NEUTRALIZATION OF SPECIAL ELEMENTS USED IN A COMMAND ('COMMAND INJECTION') CWE-77

A command injection vulnerability exists in the Aruba Instant command line interface, which may allow an attacker to fully compromise the underlying access point operating system.

CVE-2020-24635 has been assigned to this vulnerability. A CVSS v3 base score of 7.2 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H).

4.2.4    IMPROPER NEUTRALIZATION OF SPECIAL ELEMENTS USED IN A COMMAND ('COMMAND INJECTION') CWE-77

A command injection vulnerability in affected Aruba Instant versions exists, which may allow the execution of arbitrary commands as a privileged user on the underlying operating system.

CVE-2020-24636 has been assigned to this vulnerability. A CVSS v3 base score of 8.1 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H).

4.2.5    IMPROPER INPUT VALIDATION CWE-20

A vulnerability can be exploited through the PAPI protocol, resulting in a system reboot, which may allow an attacker to create a denial-of-service condition.

CVE-2021-25143 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

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

An attacker may send specially crafted packets that may allow the execution of arbitrary code as a privileged user on the underlying operating system.

CVE-2021-25144 has been assigned to this vulnerability. A CVSS v3 base score of 9.8 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

4.2.7    IMPROPER INPUT VALIDATION CWE-20

An information disclosure vulnerability exists in affected Aruba Instant access points, which may allow an unauthenticated attacker in the same wired network to access sensitive information.

CVE-2021-25145 has been assigned to this vulnerability. A CVSS v3 base score of 4.3 has been calculated; the CVSS vector string is (AV:A/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N).

4.2.8    IMPROPER NEUTRALIZATION OF SPECIAL ELEMENTS USED IN A COMMAND ('COMMAND INJECTION') CWE-77

A command injection vulnerability exists in the Aruba Instant command line interface, which may allow an attacker to fully compromise the underlying access point operating system.

CVE-2021-25146 has been assigned to this vulnerability. A CVSS v3 base score of 7.2 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H).

4.2.9    IMPROPER INPUT VALIDATION CWE-20

An attacker may overwrite an arbitrary file with attacker-controlled content via the command line interface, which may allow overwriting of sensitive system files.

CVE-2021-25148 has been assigned to this vulnerability. A CVSS v3 base score of 8.8 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

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

An attacker may send specially crafted packets that may allow the execution of arbitrary code as a privileged user on the underlying operating system.

CVE-2021-25149 has been assigned to this vulnerability. A CVSS v3 base score of 9.8 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

4.2.11    IMPROPER NEUTRALIZATION OF SPECIAL ELEMENTS USED IN A COMMAND ('COMMAND INJECTION') CWE-77

A command injection vulnerability exists in the Aruba Instant command line interface, which may allow an attacker to fully compromise the underlying host operating system.

CVE-2021-25150 has been assigned to this vulnerability. A CVSS v3 base score of 8.8 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H).

4.2.12    IMPROPER INPUT VALIDATION CWE-20

An attacker can overwrite an arbitrary file with attacker-controlled content via the web UI that may allow overwriting of sensitive system files.

CVE-2021-25155 has been assigned to this vulnerability. A CVSS v3 base score of 7.2 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H).

4.2.13    IMPROPER INPUT VALIDATION CWE-20

An arbitrary directory creation vulnerability exists in affected Aruba Instant hosts, which may allow a directory to be created with the directory name controlled by the attacker.

CVE-2021-25156 has been assigned to this vulnerability. A CVSS v3 base score of 4.9 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N).

4.2.14    IMPROPER INPUT VALIDATION CWE-20

An arbitrary file read vulnerability exists in affected Aruba Instant hosts, which may allow an attacker to read any file off the underlying file system, including sensitive system files.

CVE-2021-25157 has been assigned to this vulnerability. A CVSS v3 base score of 4.9 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N).

4.2.15    CONCURRENT EXECUTION USING SHARED RESOURCE WITH IMPROPER SYNCRONIZATION ('RACE CONDITION') CWE-362

A race condition in the web UI may allow an attacker to read arbitrary files off the underlying file system, including sensitive system files.

CVE-2021-25158 has been assigned to this vulnerability. A CVSS v3 base score of 5.9 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N).

4.2.16    IMPROPER INPUT VALIDATION CWE-20

An arbitrary file write vulnerability exists in the affected Aruba Instant using the web interface, which may allow an attacker to overwrite sensitive system files.

CVE-2021-25159 has been assigned to this vulnerability. A CVSS v3 base score of 4.4 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:H/A:N).

4.2.17   IMPROPER INPUT VALIDATION CWE-20

An arbitrary file write vulnerability exists in the Aruba Instant web UI, which may allow an attacker to write arbitrary contents to a single specific backup file and result in the corruption of the backup file.

CVE-2021-25160 has been assigned to this vulnerability. A CVSS v3 base score of 4.9 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N).

4.2.18    IMPROPER NEUTRALIZATION OF INPUT DURING WEB PAGE GENERATION ('CROSS-SITE SCRIPTING') CWE-79

An attacker may execute a reflected cross-site scripting attack against a user of the web-based management interface, which may allow an attacker to execute arbitrary script code in a victim’s browser in the context of the affected interface.

CVE-2021-25161 has been assigned to this vulnerability. A CVSS v3 base score of 6.1 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

4.2.19    IMPROPER NEUTRALIZATION OF SPECIAL ELEMENTS USED IN A COMMAND ('COMMAND INJECTION') CWE-77

An unauthenticated command injection vulnerability exists within the Aruba Instant Web UI, which may allow execution of arbitrary commands on the underlying operating system.

CVE-2021-25162 has been assigned to this vulnerability. A CVSS v3 base score of 7.5 has been calculated; the CVSS vector string is (AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H).

4.2.20    IMPROPER NEUTRALIZATION OF SCRIPT-RELATED HTML TAGS IN A WEB PAGE (BASIC XSS) CWE-80

A vulnerability in the captive portal of Aruba Instant could allow an unauthenticated remote attacker to conduct a reflected cross-site scripting (XSS) attack against another user of the portal. A successful exploit could allow an attacker to execute arbitrary script code in a victim’s browser in the context of the affected interface. 

CVE-2021-34617 has been assigned to this vulnerability. A CVSS v3 base score of 6.1 has been calculated; the CVSS vector string is (AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N).

4.2.21    UNCONTROLLED RESOURCE CONSUMPTION CWE-400

An unauthenticated denial-of-service vulnerability exists in affected Aruba Instant access points. Exploitation of this vulnerability is only possible via direct ethernet connection to the access point. This vulnerability can be exploited through the LLPD protocol and could result in the unavailability of the affected access point due to resource exhaustion. 

CVE-2021-34618 has been assigned to this vulnerability. A CVSS v3 base score of 6.5 has been calculated; the CVSS vector string is (AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

4.3 BACKGROUND

• CRITICAL INFRASTRUCTURE SECTORS: Chemical, Energy, Food and Agriculture, Healthcare and Public Health, Transportation Systems, and Water and Wastewater Systems
• COUNTRIES/AREAS DEPLOYED: Worldwide
• COMPANY HEADQUARTERS LOCATION: Germany

4.4 RESEARCHER

Siemens reported these vulnerabilities to CISA.

5. MITIGATIONS

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Siemens recommends upgrading SCALANCE W1750D to v8.7.1.3 or later

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

• Block access to the Aruba Instant device IP address on Port 8211/UDP from all untrusted users.
• Block access to the Aruba Instant Command Line Interface from all untrusted users.
• Block access to the Aruba Instant Web Management Interface from all untrusted users.

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 additional information see Siemens Security Advisory SSA-723417

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 that they are not accessible from the Internet.
• Locate control system networks and remote devices behind firewalls, and isolate them from the business network.
• 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 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.

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.

No known public exploits specifically target these vulnerabilities.

• Siemens