Emerson Liebert SiteScan XML External Entity Vulnerability


基本信息

时间: 2016-11-29

风险等级: 未知

ICSA: ICS Advisory (ICSA-16-334-01)

厂商: 未知

原地址: https://www.us-cert.gov/ics/advisories/ICSA-16-334-01


OVERVIEW

Researcher Evgeny Ermakov from Kaspersky Lab has identified an XML External Entity (XXE) vulnerability affecting Emerson’s Liebert SiteScan application. Emerson has produced patches to mitigate this vulnerability.

This vulnerability could be exploited remotely.

AFFECTED PRODUCTS

The following Liebert SiteScan versions are affected:

  • SiteScan Web Version 6.5, and prior.

IMPACT

Exploitation of this vulnerability may lead to the disclosure of confidential data, denial of service (DoS), server side request forgery, port scanning from the perspective of the machine where the parser is located, and other system impacts.

Impact to individual organizations depends on many factors that are unique to each organization. NCCIC/ICS-CERT recommends that organizations evaluate the impact of this vulnerability based on their operational environment, architecture, and product implementation.

BACKGROUND

Emerson is a US-based company that maintains offices in several countries around the world, including the US, UK, Netherlands, Italy, India, Germany, France, Czech Republic, China, and Australia.

The affected product, Liebert SiteScan, is a web-based data center monitoring application providing centralized oversight of Liebert precision air, power and UPS units, as well as many other analog or digital devices. According to Emerson, Liebert SiteScan is deployed across several sectors including Commercial Facilities, Critical Manufacturing, Energy, Water and Wastewater Systems, and others. Emerson reports that this product is used worldwide.

VULNERABILITY CHARACTERIZATION

VULNERABILITY OVERVIEW

IMPROPER RESTRICTION OF XML EXTERNAL ENTITYa

An attacker may enter malicious input to Liebert SiteScan through a weakly configured XML parser causing the application to execute arbitrary code or disclose file contents from a server or connected network.

CVE-2016-8348b has been assigned to this vulnerability. CVSSv3 base score: 7.5 has been assigned; the CVSS vector string is (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N).c

VULNERABILITY DETAILS

EXPLOITABILITY

This vulnerability could be exploited remotely.

EXISTENCE OF EXPLOIT

No known public exploits specifically target this vulnerability.

DIFFICULTY

An attacker with a low skill would be able to exploit this vulnerability.

MITIGATION

Emerson recommends that affected users update Liebert SiteScan with the following patches:

  • SiteScan Web Version 6.1, the patch file is: WS61_Security_Update.update, and
  • SiteScan Web Version 6.5, the patch file is: WS65_Security_Update.update.

These patches may be obtained by contacting Liebert Services at 1-800-543-2378.

ICS-CERT recommends that users take defensive measures to minimize the risk of exploitation of this vulnerability. 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 that VPNs may have vulnerabilities and should be updated to the most current version available. Also recognize that VPN is only as secure as the connected devices.

ICS-CERT reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.

ICS-CERT also provides a section for control systems security recommended practices on the ICS-CERT web page. 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 in the ICS‑CERT Technical Information Paper, ICS-TIP-12-146-01B--Targeted Cyber Intrusion Detection and Mitigation Strategies, that is available for download from the ICS-CERT web site.

Organizations observing any suspected malicious activity should follow their established internal procedures and report their findings to ICS-CERT for tracking and correlation against other incidents.

  • a. CWE-611: Improper Restriction of XML External Entity Reference (‘XXE’), https://cwe.mitre.org/data/definitions/611.html, web site last accessed November 29, 2016.
  • b. NVD, https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2016-8348, NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
  • c. CVSS Calculator, http://www.first.org/cvss/calculator/3.0#CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N, web site last accessed November 29, 2016.