OVERVIEW

Siemens and Positive Technology researchers (Yury Goltsev, Llya Karpov, Alexey Osipov, Dmitry Serebryannikov and Alex Timorin) have identified nine firmware vulnerabilities in the Siemens SIMATIC S7-1500 CPU Firmware. Siemens has produced a patch that mitigates these vulnerabilities.

These vulnerabilities could be exploited remotely. 

AFFECTED PRODUCTS

The following SIMATIC S7-1500 versions are affected:

• SIMATIC S7-1500 CPU family, all versions older than V1.5

IMPACT

The multiple vulnerabilities discovered in the SIMATIC S7-1500 CPU firmware may allow attackers to perform denial-of-service (DoS) attacks with specially crafted HTTP(S), ISO-TSAP, or Profinet network packets. The integrated web server may also be vulnerable to cross-site request forgery (CSRF), cross-site scripting (XSS), header injection, and open redirect attacks as well as privilege escalation. The vulnerabilities could be exploited over the network without authentication.

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

BACKGROUND

Siemens is a multinational company headquartered in Munich, Germany.

Products in the Siemens SIMATIC S7-1500 CPU family have been designed for process control in Critical Infrastructure Sectors such as Chemical, Critical Manufacturing, Energy, Food and Agriculture, and Water and Wastewater Systems.

VULNERABILITY CHARACTERIZATION

VULNERABILITY OVERVIEW

The web server of the affected PLCs (port 80/TCP and port 443/TCP) might allow CSRF attacks, compromising integrity and availability of the affected device.

Additional social engineering would be required for this exploit.

CVE-2014-2249b has been assigned to this vulnerability. A CVSS v2 base score of 5.8 has been assigned; the CVSS vector string is (AV:N/AC:M/Au:N/C:N/I:P/A:P).c

The integrated web server (Port 80/TCP and Port 443/TCP) of the affected device might be vulnerable to XSS attacks.

Additional social engineering would be required for this exploit.

CVE-2014-2246e has been assigned to this vulnerability. A CVSS v2 base score of 4.3 has been assigned; the CVSS vector string is (AV:N/AC:M/Au:N/C:N/I:P/A:N).f

The integrated web server (Port 80/TCP and Port 443/TCP) of the affected device might allow attackers to inject HTML headers.

Additional social engineering would be required for this exploit.

CVE-2014-2247h has been assigned to this vulnerability. A CVSS v2 base score of 5.8 has been assigned; the CVSS vector string is (AV:N/AC:M/Au:N/C:N/I:P/A:P).i

Because of low entropy in its random number generator, the authentication of the integrated web server (Port 80/TCP and Port 443/TCP) of S7-1500 PLCs might allow attackers to hijack web sessions over the network without authentication.

CVE-2014-2251k has been assigned to this vulnerability. A CVSS v2 base score of 8.3 has been assigned; the CVSS vector string is (AV:N/AC:M/Au:N/C:P/I:P/A:C).l

The integrated web server (Port 80/TCP and Port 443/TCP) of the affected device might allow attackers to redirect users to untrusted web sites.

Additional social engineering would be required for this exploit.

CVE-2014-2248n has been assigned to this vulnerability. A CVSS v2 base score of 4.3 has been assigned; the CVSS vector string is (AV:N/AC:M/Au:N/C:N/I:P/A:N).o

Specially crafted packets sent on Port 443/TCP (HTTPS) might cause the device to go into defect mode, effectively causing a DoS. A cold restart is required to recover the system.

CVE-2014-2259q has been assigned to this vulnerability. A CVSS v2 base score of 7.8 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:N/C:N/I:N/A:C).r

Specially crafted Profinet packets sent to the affected device might cause the device to go into defect mode, effectively causing a DoS. A cold restart is required to recover the system.

The attacker must have access to the local Ethernet segment.

CVE-2014-2253t has been assigned to this vulnerability. A CVSS v2 base score of 6.1 has been assigned; the CVSS vector string is (AV:A/AC:L/Au:N/C:N/I:N/A:C).u

Specially crafted packets sent on Port 80/TCP (HTTP) might cause the device to go into defect mode, effectively causing a DoS. A cold restart is required to recover the system.

CVE-2014-2255w has been assigned to this vulnerability. A CVSS v2 base score of 7.8 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:N/C:N/I:N/A:C).x

Specially crafted packets sent on Port 102/TCP (ISO-TSAP) might cause the device to go into defect mode, effectively causing a DoS. A cold restart is required to recover the system.

CVE-2014-2257z has been assigned to this vulnerability. A CVSS v2 base score of 7.8 has been assigned; the CVSS vector string is (AV:N/AC:L/Au:N/C:N/I:N/A:C).aa

VULNERABILITY DETAILS

EXPLOITABILITY

These vulnerabilities could be exploited remotely. Some will require additional user interaction.

EXISTENCE OF EXPLOIT

No known public exploits specifically target these vulnerabilities.

DIFFICULTY

An attacker with moderate skill would be able to exploit these vulnerabilities.

MITIGATION

Siemens addresses all these issues in a security advisory that can be found at the following location:
http://www.siemens.com/innovation/pool/de/forschungsfelder/siemens_security_advisory_ssa-456423.pdf

Siemens has provided a firmware update (V1.5.0), which fixes the reported vulnerabilities. Customers may obtain a copy of this firmware update at the following location:
http://support.automation.siemens.com/WW/view/en/88613339

Siemens strongly recommends protecting network access to S7-1500 CPUs with appropriate mechanisms. Siemens advises following recommended security practices and configuring the environment according to operational guidelines in order to run the devices in a protected IT environment.
http://www.industry.siemens.com/topics/global/en/industrial-security/Documents/operational_guidelines_industrial_security_en.pdf

Siemens recommends operating the devices only within trusted networks (Information about Industrial Security by Siemens):
http://www.siemens.com/industrialsecurity

ICS-CERT encourages asset owners to take additional defensive measures to protect against this and other cybersecurity risks.

• 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 VPN is only as secure as the connected devices.

ICS-CERT also provides a section for control systems security recommended practices on the ICS-CERT web page at: http://ics-cert.us-cert.gov/content/recommended-practices. Several recommended practices are available for reading and download, including Improving Industrial Control Systems Cybersecurity with Defense-in-Depth Strategies. ICS-CERT reminds organizations to perform proper impact analysis and risk assessment prior to deploying defensive measures.

Additional mitigation guidance and recommended practices are publicly available in the ICS‑CERT Technical Information Paper, ICS-TIP-12-146-01B—Targeted Cyber Intrusion Mitigation Strategies, that is available for download from the ICS-CERT web site (http://ics-cert.us-cert.gov/).

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.

In addition, ICS-CERT recommends that users take the following measures to protect themselves from social engineering attacks:

1. Do not click web links or open unsolicited attachments in email messages.
2. Refer to Recognizing and Avoiding Email Scamsbb for more information on avoiding email scams.
3. Refer to Avoiding Social Engineering and Phishing Attackscc for more information on social engineering attacks.

• a. CWE-352: Cross-Site Request Forgery, http://cwe.mitre.org/data/definitions/352.html, web site last accessed March 14, 2014.
• b. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2249 , 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://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:M/Au:N/C:N/I:P/A:P, web site last accessed March 14, 2014.
• d. CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS), http://cwe.mitre.org/data/definitions/80.html, web site last accessed March 14, 2014.
• e. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2246 , NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
• f. CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:M/Au:N/C:N/I:P/A:N, web site last accessed March 14, 2014.
• g. CWE-80: Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS), http://cwe.mitre.org/data/definitions/80.html, web site last accessed March 14, 2014.
• h. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2247 , NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
• i. CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:M/Au:N/C:N/I:P/A:P, web site last accessed March 14, 2014.
• j. CWE-331: Insufficient Entropy, http://cwe.mitre.org/data/definitions/331.html, web site last accessed March 14, 2014.
• k. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2251 , NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
• l. CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:M/Au:N/C:P/I:P/A:C, web site last accessed March 14, 2014.
• m. CWE-601: URL Redirection to Untrusted Site (“Open Redirect”), http://cwe.mitre.org/data/definitions/601.html, web site last accessed March 14, 2014.
• n. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2248, NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
• o. CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:M/Au:N/C:N/I:P/A:N, web site last accessed March 14, 2014.
• p. CWE-404: Improper Resource Shutdown or Release, http://cwe.mitre.org/data/definitions/404.html, web site last accessed March 14, 2014.
• q. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2259 , NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
• r. CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:L/Au:N/C:N/I:N/A:C, web site last accessed March 14, 2014.
• s. CWE-404: Improper Resource Shutdown or Release, http://cwe.mitre.org/data/definitions/404.html, web site last accessed March 14, 2014.
• t. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2253, NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
• u. CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:A/AC:L/Au:N/C:N/I:N/A:C, web site last accessed March 14, 2014.
• v. CWE-404: Improper Resource Shutdown or Release, http://cwe.mitre.org/data/definitions/404.html, web site last accessed March 14, 2014.
• w. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2255 , NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
• x. CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:L/Au:N/C:N/I:N/A:C, web site last accessed March 14, 2014.
• y. CWE-404: Improper Resource Shutdown or Release, http://cwe.mitre.org/data/definitions/404.html, web site last accessed March 14, 2014.
• z. NVD, http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-2257 , NIST uses this advisory to create the CVE web site report. This web site will be active sometime after publication of this advisory.
• aa. CVSS Calculator, http://nvd.nist.gov/cvss.cfm?version=2&vector=AV:N/AC:L/Au:N/C:N/I:N/A:C, web site last accessed March 14, 2014.
• bb. Recognizing and Avoiding Email Scams, http://www.us-cert.gov/reading_room/emailscams_0905.pdf, web site last accessed March 14, 2014.
• cc. National Cyber Alert System Cyber Security Tip ST04-014, http://www.us-cert.gov/cas/tips/ST04-014.html, web site last accessed March 14, 2014.