Hackers have exploited a severe vulnerability in PHP (CVE-2024-4577) to deploy a previously unknown backdoor named Msupedge, targeting an unnamed university in Taiwan. This vulnerability, with a CVSS score of 9.8, allows remote code execution, providing an entry point for attackers. Once inside, the threat actors installed Msupedge, a dynamic-link library (DLL) backdoor, in system paths such as “csidl_drive_fixed\xampp” and “csidl_system\wbem”. The DLL files include wuplog.dll, which is launched by the Apache HTTP server. The specific method used to initiate the second DLL remains unclear, adding a layer of complexity to the attack.
Msupedge is notable for its use of DNS tunneling to communicate with its command-and-control (C&C) server. This technique, based on the open-source dnscat2 tool, allows the backdoor to receive commands via DNS traffic. The backdoor’s operation hinges on the resolved IP address of the C&C server (ctl.msedeapi[.]net), where the third octet of the IP address acts as a switch case to determine the backdoor’s behavior. For example, if the third octet is 145, it translates to 138 (0x8a), triggering specific responses such as creating processes or downloading files.
Commands executed by Msupedge include creating processes using commands from DNS TXT records, downloading files via URLs received through DNS TXT records, and managing temporary files. The backdoor can also pause operations for predetermined intervals or delete temporary files, adding flexibility to the attacker’s control. This sophisticated approach highlights the evolving tactics of cybercriminals and the need for advanced detection and mitigation strategies.
The emergence of Msupedge comes amidst other cyber threats, such as a new phishing campaign linked to the UTG-Q-010 threat group, which distributes the open-source Pupy RAT malware. This malware campaign uses malicious .lnk files with embedded DLL loaders to deploy Pupy RAT, a Python-based Remote Access Trojan (RAT). The combination of these attacks underscores the critical need for organizations to address vulnerabilities promptly and enhance their cybersecurity defenses to protect against such complex and evolving threats.
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