Siemens Desigo PXC and DXR Devices (Update A)
1. EXECUTIVE SUMMARY
- CVSS v3 9.0
- ATTENTION: Exploitable remotely/low attack complexity
- Vendor: Siemens
- Equipment: PXC and DXR Devices
- Vulnerabilities: Special Element Injection, Uncontrolled Resource Consumption, Use of Password Hash with Insufficient Computational Effort, Insufficient Session Expiration, Observable Discrepancy, Improper Restriction of Excessive Authentication Attempts, Sensitive Cookie in HTTPS Session Without ‘Secure’ Attribute, Uncaught Exception
2. UPDATE INFORMATION
This updated advisory is a follow-up to the advisory update titled ICSA-21-132-10 Siemens SIMATIC WinCC (Update A) that was published May 12, 2022, to the ICS webpage at cisa.gov/ics.
3. RISK EVALUATION
Successful exploitation of these vulnerabilities could allow an attacker to potentially intercept unencrypted transmission of sensitive information, cause a denial-of-service condition, perform remote code execution, or disable and reset a device to factory state.
4. TECHNICAL DETAILS
4.1 AFFECTED PRODUCTS
Siemens reports this vulnerability affects the following Desigo DXR and PXC controllers:
• Desigo DXR2: All versions prior to v01.21.142.5-22
• Desigo PXC3: All versions prior to v01.21.142.4-18
• Desigo PXC4: All versions prior to v02.20.142.10-10884
• Desigo PXC5: All versions prior to v02.20.142.10-10884
4.2 VULNERABILITY OVERVIEW
4.2.1 FAILURE TO SANITIZE SPECIAL ELEMENTS INTO A DIFFERENT PLANE (SPECIAL ELEMENT INJECTION) CWE-75
The web application fails to enforce an upper bound to the cost factor of the PBKDF2 derived key during the creation or update of an account. An attacker with the user profile access privilege could cause a denial-of-service condition through CPU consumption by setting a PBKDF2 derived key with a high-cost effort, followed by a login attempt to the modified account.
The web application stores the PBKDF2 derived key of user’s passwords with a low iteration count. An attacker with user profile access privilege can retrieve the stored password hashes of other accounts and then successfully perform an offline cracking attack and recover the plaintext passwords of other users.
The web application returns an AuthToken that does not expire at the defined auto logoff delay timeout. An attacker could capture this token and re-use old session credentials or session IDs for authorization.
The login functionality of the application fails to normalize the response times of login attempts performed with wrong usernames with the ones executed with correct usernames. A remote unauthenticated attacker could exploit this side-channel information to perform a username enumeration attack and identify valid usernames.
The login functionality of the application does not employ countermeasures against password spraying attacks or credential stuffing attacks. An attacker could obtain a list of valid usernames on the device and use that list to perform a precise password spraying or credential stuffing attack to obtain access to at least one account.
When the controller receives a specific BACnet protocol packet, an exception causes the BACnet communication function to go into a “out of work” state and could result in the controller going into a “factory reset” state.
- CRITICAL INFRASTRUCTURE SECTORS: Multiple Sectors
- COUNTRIES/AREAS DEPLOYED: Worldwide
- COMPANY HEADQUARTERS LOCATION: Germany
Andrea Palanca, of Nozomi Networks, reported these vulnerabilities to CISA.
Siemens recommends updating to the latest software version:
--------- Begin Update A Part 1 of 1 ---------
- Desigo DXR2: Update to v01.21.142.5-22 or later
- Desigo PXC3: Update to v01.21.142.4-18 or later
- Desigo PXC4: Update to v02.20.142.10-10884 or later
- Desigo PXC5: Update to v02.20.142.10-10884 or later
--------- End Update A Part 1 of 1 ---------
Contact Siemens for update information.
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 the recommendations in the product manuals.
For additional information, please refer to Siemens Security Advisory SSA-626968
For additional information, please refer to Siemens Security Advisory SSA-662649
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 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 cisa.gov/ics. 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 cisa.gov/ics 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.