Pierluigi Paganini October 14, 2024

An alleged nation-state actor exploited three zero-day vulnerabilities in Ivanti Cloud Service Appliance (CSA) in recent attacks.

Fortinet FortiGuard Labs researchers warn that a suspected nation-state actor has been exploiting three Ivanti Cloud Service Appliance (CSA) zero-day issues to carry out malicious activities.

The three vulnerabilities exploited by the threat actor are:

• CVE-2024-9380 (CVSS score: 7.2) – an OS command injection vulnerability in the admin web console of Ivanti CSA before version 5.0.2. A remote authenticated attacker with admin privileges can exploit the vulnerability to achieve remote code execution.
• CVE-2024-8190 (CVSS score: 7.2) – A command injection vulnerability in Ivanti Cloud Services Appliance versions 4.6 Patch 518 and before. A remote authenticated attacker can exploit the flaw to obtain remote code execution. The attacker must have admin level privileges to exploit this vulnerability. 
• CVE-2024-8963 (CVSS score: 9.4) – A path traversal vulnerability in the Ivanti CSA before 4.6 Patch 519. A remote, unauthenticated attacker can exploit the vulnerability to access restricted functionality. 

“an advanced adversary was observed exploiting three vulnerabilities affecting the Ivanti Cloud Services Appliance (CSA). At the time of our investigation, two out of the three identified vulnerabilities were not publicly known. This incident is a prime example of how threat actors chain zero-day vulnerabilities to gain initial access to a victim’s network.” reads the advisory published by Fortinet.

Threat actors exploited the zero-day flaws to gain unauthenticated access to the CSA, enumerate users configured in the CSA appliance, and attempt to access their credentials. Then, once obtained gsbadmin and admin credentials, attackers used them to exploit a command injection flaw in /gsb/reports.php, and deploy a web shell (“help.php”).

“Command injection was found to be exploited in the following format, where a php script /subin/tripwire was executed with the parameter –update, followed by a semicolon and a malicious command.” reads the advisory.

“The first malicious command injected by the threat actor was used to create a web shell called help.php in the CSA webroot folder under the /gsb directory.”

On September 10, 2024, after Ivanti released an advisory for CVE-2024-8190, a threat actor still in the victim’s network “patched” exploited command injection vulnerabilities in DateTimeTab.php and reports.php, likely to prevent other intruders from exploiting them. The actor replaced semicolons with underscores in the POST parameters TW_ID and TIMEZONE, rendering these vulnerabilities ineffective. This technique, confirmed through testing, shows the threat actor’s intent to secure exclusive access to the compromised environment.

The threat actor created multiple web shells and altered the legitimate syslog.php file by appending malicious code, converting it into a web shell for further exploitation.

During memory analysis, Fortinet researchers found evidence that the threat actor used a ReverseSocks5 proxy tool for internal network attacks via the CSA appliance. On September 7, 2024, logs revealed an attempt to deploy a Linux kernel module rootkit on the compromised systems, likely to maintain persistent access, even after a factory reset. This aligns with reports of Ivanti CSA appliance compromises.

“The advanced adversaries were observed exploiting and chaining zero-day vulnerabilities to establish beachhead access in the victim’s network. You can read more about the Ivanti CSA zero-day attack in our Threat Signal Report: https://www.fortiguard.com/threat-signal-report/5556.” concludes the report.

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Pierluigi Paganini

(SecurityAffairs – hacking, Ivanti CSA)