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Best Practices • Apply patches as soon as possible • Disable unnecessary ports and protocols • Replace end-of-life infrastructure • Implement a centralized patch management system

This joint Cybersecurity Advisory describes the ways in which People’s Republic of China (PRC) state-sponsored cyber actors continue to exploit publicly known vulnerabilities in order to establish a broad network of compromised infrastructure. These actors use the network to exploit a wide variety of targets worldwide, including public and private sector organizations. The advisory details the targeting and compromise of major telecommunications companies and network service providers and the top vulnerabilities—primarily Common Vulnerabilities and Exposures (CVEs)—associated with network devices routinely exploited by the cyber actors since 2020.

This joint Cybersecurity Advisory was coauthored by the National Security Agency (NSA), the Cybersecurity and Infrastructure Security Agency (CISA), and the Federal Bureau of Investigation (FBI). It builds on previous NSA, CISA, and FBI reporting to inform federal and state, local, tribal, and territorial (SLTT) government; critical infrastructure (CI), including the Defense Industrial Base (DIB); and private sector organizations about notable trends and persistent tactics, techniques, and procedures (TTPs).

Entities can mitigate the vulnerabilities listed in this advisory by applying the available patches to their systems, replacing end-of-life infrastructure, and implementing a centralized patch management program.

NSA, CISA, and the FBI urge U.S. and allied governments, CI, and private industry organizations to apply the recommendations listed in the Mitigations section and Appendix A: Vulnerabilities to increase their defensive posture and reduce the risk of PRC state-sponsored malicious cyber actors affecting their critical networks.

For more information on PRC state-sponsored malicious cyber activity, see CISA’s China Cyber Threat Overview and Advisories webpage.

PRC state-sponsored cyber actors readily exploit vulnerabilities to compromise unpatched network devices. Network devices, such as Small Office/Home Office (SOHO) routers and Network Attached Storage (NAS) devices, serve as additional access points to route command and control (C2) traffic and act as midpoints to conduct network intrusions on other entities. Over the last few years, a series of high-severity vulnerabilities for network devices provided cyber actors with the ability to regularly exploit and gain access to vulnerable infrastructure devices. In addition, these devices are often overlooked by cyber defenders, who struggle to maintain and keep pace with routine software patching of Internet-facing services and endpoint devices.

Since 2020, PRC state-sponsored cyber actors have conducted widespread campaigns to rapidly exploit publicly identified security vulnerabilities, also known as common vulnerabilities and exposures (CVEs). This technique has allowed the actors to gain access into victim accounts using publicly available exploit code against virtual private network (VPN) services [T1133]  or public facing applications [T1190]—without using their own distinctive or identifying malware—so long as the actors acted before victim organizations updated their systems. 

PRC state-sponsored cyber actors typically conduct their intrusions by accessing compromised servers called hop points from numerous China-based Internet Protocol (IP) addresses resolving to different Chinese Internet service providers (ISPs). The cyber actors typically obtain the use of servers by leasing remote access directly or indirectly from hosting providers. They use these servers to register and access operational email accounts, host C2 domains, and interact with victim networks. Cyber actors use these hop points as an obfuscation technique when interacting with victim networks.

These cyber actors are also consistently evolving and adapting tactics to bypass defenses. NSA, CISA, and the FBI have observed state-sponsored cyber actors monitoring network defenders’ accounts and actions, and then modifying their ongoing campaign as needed to remain undetected. Cyber actors have modified their infrastructure and toolsets immediately following the release of information related to their ongoing campaigns. PRC state-sponsored cyber actors often mix their customized toolset with publicly available tools, especially by leveraging tools that are native to the network environment, to obscure their activity by blending into the noise or normal activity of a network.

NSA, CISA, and the FBI consider the common vulnerabilities and exposures (CVEs) listed in Table 1 to be the network device CVEs most frequently exploited by PRC state-sponsored cyber actors since 2020.

Table 1: Top network device CVEs exploited by PRC state-sponsored cyber actors

PRC state-sponsored cyber actors frequently utilize open-source tools for reconnaissance and vulnerability scanning. The actors have utilized open-source router specific software frameworks, RouterSploit and RouterScan [T1595.002], to identify makes, models, and known vulnerabilities for further investigation and exploitation. The RouterSploit Framework is an open-source exploitation framework dedicated to embedded devices. RouterScan is an open-source tool that easily allows for the scanning of IP addresses for vulnerabilities. These tools enable exploitation of SOHO and other routers manufactured by major industry providers, including Cisco, Fortinet, and MikroTik.

Upon gaining an initial foothold into a telecommunications organization or network service provider, PRC state-sponsored cyber actors have identified critical users and infrastructure including systems critical to maintaining the security of authentication, authorization, and accounting. After identifying a critical Remote Authentication Dial-In User Service (RADIUS) server, the cyber actors gained credentials to access the underlying Structured Query Language (SQL) database [T1078] and utilized SQL commands to dump the credentials [T1555], which contained both cleartext and hashed passwords for user and administrative accounts. 

Having gained credentials from the RADIUS server, PRC state-sponsored cyber actors used those credentials with custom automated scripts to authenticate to a router via Secure Shell (SSH), execute router commands, and save the output [T1119]. These scripts targeted Cisco and Juniper routers and saved the output of the executed commands, including the current configuration of each router. After successfully capturing the command output, these configurations were exfiltrated off network to the actor’s infrastructure [TA0010]. The cyber actors likely used additional scripting to further automate the exploitation of medium to large victim networks, where routers and switches are numerous, to gather massive numbers of router configurations that would be necessary to successfully manipulate traffic within the network.

Armed with valid accounts and credentials from the compromised RADIUS server and the router configurations, the cyber actors returned to the network and used their access and knowledge to successfully authenticate and execute router commands to surreptitiously route [T1599], capture [T1020.001], and exfiltrate traffic out of the network to actor-controlled infrastructure. 

While other manufacturers likely have similar commands, the cyber actors executed the following commands on a Juniper router to perform initial tunnel configuration for eventual exfiltration out of the network:

After establishing the tunnel, the cyber actors configured the local interface on the device and updated the routing table to route traffic to actor-controlled infrastructure.

PRC state-sponsored cyber actors then configured port mirroring to copy all traffic to the local interface, which was subsequently forwarded through the tunnel out of the network to actor-controlled infrastructure. 

Having completed their configuration changes, the cyber actors often modified and/or removed local log files to destroy evidence of their activity to further obfuscate their presence and evade detection.

PRC state-sponsored cyber actors also utilized command line utility programs like PuTTY Link (Plink) to establish SSH tunnels [T1572] between internal hosts and leased virtual private server (VPS) infrastructure. These actors often conducted system network configuration discovery [T1016.001] on these host networks by sending hypertext transfer protocol (HTTP) requests to C2 infrastructure in order to illuminate the external public IP address.

NSA, CISA, and the FBI urge organizations to apply the following recommendations as well as the mitigation and detection recommendations in Appendix A, which are tailored to observed tactics and techniques. While some vulnerabilities have specific additional mitigations below, the following mitigations generally apply:

Refer to us-cert.cisa.gov/china, https://www.ic3.gov/Home/IndustryAlerts, and https://www.nsa.gov/cybersecurity-guidance for previous reporting on People’s Republic of China state-sponsored malicious cyber activity.

U.S. government and critical infrastructure organizations, should consider signing up for CISA’s cyber hygiene services, including vulnerability scanning, to help reduce exposure to threats.

U.S. Defense Industrial Base (DIB) organizations, should consider signing up for the NSA Cybersecurity Collaboration Center’s DIB Cybersecurity Service Offerings, including Protective Domain Name System (PDNS) services, vulnerability scanning, and threat intelligence collaboration. For more information on eligibility criteria and how to enroll in these services, email dib_defense@cyber.nsa.gov.

To report incidents and anomalous activity or to request incident response resources or technical assistance related to these threats, contact CISA at report@cisa.gov. To report computer intrusion or cybercrime activity related to information found in this advisory, contact your local FBI field office at www.fbi.gov/contact-us/field, or the FBI’s 24/7 Cyber Watch at 855-292-3937 or by email at CyWatch@fbi.gov. For NSA client requirements or general cybersecurity inquiries, contact Cybersecurity_Requests@nsa.gov. 

The information and opinions contained in this document are provided "as is" and without any warranties or guarantees. Reference herein to any specific commercial products, process, or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorsement, recommendation, or favoring by the United States Government, and this guidance shall not be used for advertising or product endorsement purposes.

This advisory was developed by NSA, CISA, and the FBI in furtherance of their respective cybersecurity missions, including their responsibilities to develop and issue cybersecurity specifications and mitigations. This information may be shared broadly to reach all appropriate stakeholders. 

Table 2: Information on Cisco CVE-2018-0171

A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition, or to execute arbitrary code on an affected device. The vulnerability is due to improper validation of packet data. An attacker could exploit this vulnerability by sending a crafted Smart Install message to an affected device on TCP port 4786. A successful exploit could allow the attacker to cause a buffer overflow on the affected device, which could have the following impacts: Triggering a reload of the device, Allowing the attacker to execute arbitrary code on the device, causing an indefinite loop on the affected device that triggers a watchdog crash.

The vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS or IOS XE software and have the smart install client feature enabled. Only smart install client switches are affected by this vulnerability described in this advisory. 

http://www.securityfocus.com/bid/103538 https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-smi2 https://ics-cert.us-cert.gov/advisories/ICSA-18-107-04 https://ics-cert.us-cert.gov/advisories/ICSA-18-107-05 https://www.darkreading.com/perimeter/attackers-exploit-cisco-switch-issue-as-vendor-warns-of-yet-another-critical-flaw/d/d-id/1331490 http://www.securitytracker.com/id/1040580

Table 3: Information on Cisco CVE-2019-15271

A vulnerability in the web-based management interface of certain Cisco Small Business RV Series Routers could allow an authenticated, remote attacker to execute arbitrary commands with root privileges. The attacker must have either a valid credential or an active session token. The vulnerability is due to lack of input validation of the HTTP payload. An attacker could exploit this vulnerability by sending a malicious HTTP request to the web-based management interface of the targeted device. A successful exploit could allow the attacker to execute commands with root privileges.

This vulnerability affects the following Cisco Small Business RV Series Routers if they are running a firmware release earlier than 4.2.3.10:

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20191106-sbrv-cmd-x

Table 4: Information on Cisco CVE-2019-1652

A vulnerability in the web-based management interface of Cisco Small Business RV320 and RV325 Dual Gigabit WAN VPN Routers could allow an authenticated, remote attacker with administrative privileges on an affected device to execute arbitrary commands. The vulnerability is due to improper validation of user-supplied input. An attacker could exploit this vulnerability by sending malicious HTTP POST requests to the web-based management interface of an affected device. A successful exploit could allow the attacker to execute arbitrary commands on the underlying Linux shell as root. Cisco has released firmware updates that address this vulnerability.

This vulnerability affects Cisco Small Business RV320 and RV325 Dual Gigabit WAN VPN Routers running firmware releases 1.4.2.15 through 1.4.2.20.

http://www.securityfocus.com/bid/106728 https://seclists.org/bugtraq/2019/Mar/55 https://www.exploit-db.com/exploits/46243/ https://www.exploit-db.com/exploits/46655/ http://seclists.org/fulldisclosure/2019/Mar/61 http://packetstormsecurity.com/files/152262/Cisco-RV320-Command-Injection.html http://packetstormsecurity.com/files/152305/Cisco-RV320-RV325-Unauthenticated-Remote-Code-Execution.html https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190123-rv-inject

Table 5: Information on Citrix CVE-2019-19781

An issue was discovered in Citrix Application Delivery Controller (ADC) and Gateway 10.5, 11.1, 12.0, 12.1, and 13.0. They allow Directory Traversal.

The vulnerability affects the following Citrix product versions on all supported platforms:

https://support.citrix.com/article/CTX267027

Table 6: Information on DrayTek CVE-2020-8515

DrayTek Vigor2960 1.3.1_Beta, Vigor3900 1.4.4_Beta, and Vigor300B 1.3.3_Beta, 1.4.2.1_Beta, and 1.4.4_Beta devices allow remote code execution as root (without authentication) via shell metacharacters to the cgi-bin/mainfunction.cgi URI. This issue has been fixed in Vigor3900/2960/300B v1.5.1.

https://draytek.com/about/security-advisory/vigor3900-/-vigor2960-/-vigor300b-router-web-management-page-vulnerability-(cve-2020-8515)/ http://packetstormsecurity.com/files/156979/DrayTek-Vigor2960-Vigor3900-Vigor300B-Remote-Command-Execution.html https://sku11army.blogspot.com/2020/01/draytek-unauthenticated-rce-in-draytek.html

Table 7: Information on D-Link CVE-2019-16920

Unauthenticated remote code execution occurs in D-Link products such as DIR-655C, DIR-866L, DIR-652, and DHP-1565. The issue occurs when the attacker sends an arbitrary input to a "PingTest" device common gateway interface that could lead to common injection. An attacker who successfully triggers the command injection could achieve full system compromise. Later, it was independently found that these are also affected: DIR-855L, DAP-1533, DIR-862L, DIR-615, DIR-835, and DIR-825.

https://www.kb.cert.org/vuls/id/766427 https://fortiguard.com/zeroday/FG-VD-19-117 https://medium.com/@80vul/determine-the-device-model-affected-by-cve-2019-16920-by-zoomeye-bf6fec7f9bb3 https://www.seebug.org/vuldb/ssvid-98079

Table 8: Information on Fortinet CVE-2018-13382

An Improper Authorization vulnerability in Fortinet FortiOS 6.0.0 to 6.0.4, 5.6.0 to 5.6.8 and 5.4.1 to 5.4.10 and FortiProxy 2.0.0, 1.2.0 to 1.2.8, 1.1.0 to 1.1.6, 1.0.0 to 1.0.7 under SSL VPN web portal allows an unauthenticated attacker to modify the password of an SSL VPN web portal user via specially crafted HTTP requests.

This vulnerability affects the following products: 

FortiOS products are vulnerable only if the SSL VPN service (web-mode or tunnel-mode) is enabled and users with local authentication.

https://fortiguard.com/psirt/FG-IR-18-389 https://fortiguard.com/advisory/FG-IR-18-389 https://www.fortiguard.com/psirt/FG-IR-20-231

Table 9: Information on Mikrotik CVE-2018-14847

MikroTik RouterOS through 6.42 allows unauthenticated remote attackers to read arbitrary files and remote authenticated attackers to write arbitrary files due to a directory traversal vulnerability in the WinBox interface.

This vulnerability affected the following MikroTik products:

https://blog.mikrotik.com/security/winbox-vulnerability.html

Table 10: Information on Netgear CVE-2017-6862

NETGEAR WNR2000v3 devices before 1.1.2.14, WNR2000v4 devices before 1.0.0.66, and WNR2000v5 devices before 1.0.0.42 allow authentication bypass and remote code execution via a buffer overflow that uses a parameter in the administration webapp. The NETGEAR ID is PSV-2016-0261.

This vulnerability affects the following products:

https://kb.netgear.com/000038542/Security-Advisory-for-Unauthenticated-Remote-Code-Execution-on-Some-Routers-PSV-2016-0261 https://www.on-x.com/sites/default/files/on-x_-_security_advisory_-_netgear_wnr2000v5_-_cve-2017-6862.pdf http://www.securityfocus.com/bid/98740

Table 11: Information on Pulse CVE-2019-11510

In Pulse Secure Pulse Connect Secure (PCS) 8.2 before 8.2R12.1, 8.3 before 8.3R7.1, and 9.0 before 9.0R3.4, an unauthenticated remote attacker can send a specially crafted URI to perform an arbitrary file reading vulnerability. 

This vulnerability affects the following Pulse Connect Secure products:

https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44101/

Table 12: Information on Pulse CVE-2021-22893

Pulse Connect Secure 9.0R3/9.1R1 and higher is vulnerable to an authentication bypass vulnerability exposed by the Windows File Share Browser and Pulse Secure Collaboration features of Pulse Connect Secure that can allow an unauthenticated user to perform remote arbitrary code execution on the Pulse Connect Secure gateway. This vulnerability has been exploited in the wild.

This vulnerability affects Pulse Connect Secure 9.0R3/9.1R1 and higher.

https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44101/ https://blog.pulsesecure.net/pulse-connect-secure-security-update/ https://kb.cert.org/vuls/id/213092 https://kb.pulsesecure.net/articles/Pulse_Security_Advisories/SA44784/ https://www.fireeye.com/blog/threat-research/2021/04/suspected-apt-actors-leverage-bypass-techniques-pulse-secure-zero-day.html

Table 13: Information on QNAP CVE-2019-7192

This improper access control vulnerability allows remote attackers to gain unauthorized access to the system. To fix these vulnerabilities, QNAP recommend updating Photo Station to their latest versions.

Update Photo Station to versions: 

This vulnerability affects QNAP Photo Station versions 5.2.11, 5.4.9, 5.7.10, and 6.0.3 or earlier.

https://www.qnap.com/zh-tw/security-advisory/nas-201911-25 http://packetstormsecurity.com/files/157857/QNAP-QTS-And-Photo-Station-6.0.3-Remote-Command-Execution.html

Table 14: Information on QNAP CVE- 2019-7193

This improper input validation vulnerability allows remote attackers to inject arbitrary code to the system. To fix the vulnerability, QNAP recommend updating QTS to their latest versions.

This vulnerability affects QNAP QTS 4.3.6 and 4.4.1 or earlier.

https://www.qnap.com/zh-tw/security-advisory/nas-201911-25 http://packetstormsecurity.com/files/157857/QNAP-QTS-And-Photo-Station-6.0.3-Remote-Command-Execution.html

Table 15: Information on QNAP CVE-2019-7194

This external control of file name or path vulnerability allows remote attackers to access or modify system files. To fix the vulnerability, QNAP recommend updating Photo Station to their latest versions.

Update Photo Station to versions: 

This vulnerability affects QNAP Photo Station versions 5.2.11, 5.4.9, 5.7.10, and 6.0.3 or earlier.

https://www.qnap.com/zh-tw/security-advisory/nas-201911-25  http://packetstormsecurity.com/files/157857/QNAP-QTS-And-Photo-Station-6.0.3-Remote-Command-Execution.html

Table 16: Information on QNAP CVE-2019-7195

This external control of file name or path vulnerability allows remote attackers to access or modify system files. To fix the vulnerability, QNAP recommend updating Photo Station to their latest versions.

Update Photo Station to versions: 

This vulnerability affects QNAP Photo Station versions 5.2.11, 5.4.9, 5.7.10, and 6.0.3 or earlier.

https://www.qnap.com/zh-tw/security-advisory/nas-201911-25 http://packetstormsecurity.com/files/157857/QNAP-QTS-And-Photo-Station-6.0.3-Remote-Command-Execution.html

Table 17: Information on Zyxel CVE-2020-29583

Firmware version 4.60 of Zyxel USG devices contains an undocumented account (zyfwp) with an unchangeable password. The password for this account can be found in cleartext in the firmware. This account can be used by someone to login to the SSH server or web interface with admin privileges.

This vulnerability affects the following technologies and versions:

http://ftp.zyxel.com/USG40/firmware/USG40_4.60(AALA.1)C0_2.pdf https://businessforum.zyxel.com/discussion/5252/zld-v4-60-revoke-and-wk48-firmware-release https://businessforum.zyxel.com/discussion/5254/whats-new-for-zld4-60-patch-1-available-on-dec-15 https://www.eyecontrol.nl/blog/undocumented-user-account-in-zyxel-products.html https://www.zyxel.com/support/CVE-2020-29583.shtml https://www.zyxel.com/support/security_advisories.shtml

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