On May 31, a critical unpatched vulnerability, which affects all confluence server and data center supported versions was reported to Atlassian by Volexity, a security company.
Atlassian warned their customers of the critical vulnerability on June 2 and issued a patch a day later. CISA added this vulnerability to their list of Known Exploited Vulnerabilities on June 3.
Check Point released a dedicated protection to prevent an attack exploiting this vulnerability and advises customers to patch the affected systems.
The vulnerability in the Atlassian Confluence and Data Center, designated as CVE-2022-26134, may lead to an unauthenticated Object-Graph Navigation Language (OGNL) expression injection attack.
A remote, unauthenticated attacker can use this vulnerability to execute arbitrary code on the target server by placing a malicious payload in the URI.
In The Wild Exploitation
Check Point Research (CPR) researchers noticed a large number of exploitations attempts since the vulnerability was published. At first, many of the would-be attackers used scanning methods to identify vulnerable targets. After a few days, the attackers started to use the vulnerability to download malware to the affected systems.
Among the exploitation logs, researchers noticed a few malicious payloads that are related to the same campaign and that originated from the same source but targeted different platforms: Linux and Windows.
The infection chain depends on the victim’s operating system.
The Linux OS Targeted Attack
The attacker utilized the Atlassian 0-day vulnerability by sending a crafted HTTP request to the victim.
The base64 string decodes into another base64 encoded string. Overall, researchers had to decode the string a few times to get the actual payload.
This script downloads a bash script file called xms from the remote C&C server to the victim’s tmp folder, executes it, and deletes it afterward.
The xms file is a dropper script. It uninstalls running agents from the victim’s machine and adds itself to cron jobs to maintain persistence upon reboot.
In addition, a network connectivity test to a[.]oracleservice.top is performed constantly.
In an attempt to spread to other machines, the script searches for ssh keys and tries to connect. It then downloads the xms file from the C&C server and executes it.
The script downloads an elf executable file called dbused to the tmp folder in various remote IPs.
The dbused file is packed using upx to avoid static detection.
The elf file is a crypto miner that exhausts the victim machine’s resources:
The Windows OS Targeted Attack
The attacker utilized the Atlassian vulnerability to execute a PowerShell download cradle to initiate a fileless attack from a remote C&C server.
The lol.ps1 script is injected to a PowerShell memory process.
The script verifies the processor’s architecture, using wmi to check whether it matches its requirements.
It then downloads an executable file called checkit2 to the tmp folder and runs it in hidden mode.
The checkit2.exe process spawns a child process, called InstallUtil.exe, which connects to the C&C server. The InstallUtil.exe in turn spawns another child process child process, AddInProcess.exe, which is the crypto miner. After a few moments of running on the victim’s machine, the checkit2 process terminates itself.
The malware downloads a new copy of itself, with a new name, to the Start Menu folder.
The crypto miner now runs on the machine and exhausts all the system’s resources:
Both attack scenarios start with an initial crafted HTTP request exploiting the CVE-2022-26134 vulnerability. The attacker executes commands using the Java execution function to download a malicious payload to the victim’s machine.
The malicious payload then downloads an executable file according to the affected OS. Both executables run a crypto miner to utilize the victim’s resources for their own benefit.
The a[.]oracleservice.top domain and the crypto wallet we extracted from the system are related to a cybercriminal group called the “8220 gang”.
Check Point Protections:
Atlassian Confluence Remote Code Execution (CVE-2022-26134)