Cybersecurity researchers have unveiled a novel technique exploiting a critical security flaw in Apache ActiveMQ, identified as CVE-2023-46604 with a high CVSS score of 10.0. This vulnerability, now actively exploited by ransomware groups deploying threats like HelloKitty and a variant similar to TellYouThePass, enables arbitrary code execution in memory.
Apache promptly addressed the issue in ActiveMQ versions 5.15.16, 5.16.7, 5.17.6, and 5.18.3 released last month, indicating the urgency of implementing the provided patches.
VulnCheck, in its latest findings, reveals that threat actors leveraging the flaw are relying on a public proof-of-concept (PoC) exploit disclosed on October 25, 2023. Exploiting the ClassPathXmlApplicationContext within ActiveMQ, attackers load a malicious XML bean configuration file over HTTP, achieving unauthenticated remote code execution on the server.
Despite characterizing this method as noisy, VulnCheck engineers a more sophisticated exploit using the FileSystemXmlApplicationContext class, embedding a specially crafted SpEL expression, and achieving the same results, including obtaining a reverse shell. While this approach allows threat actors to avoid dropping tools to disk, it triggers an exception message in the activemq.log file, emphasizing the importance for attackers to clean up the forensic trail.
In light of these developments, Jacob Baines, chief technology officer at VulnCheck, underscores the critical need to promptly patch ActiveMQ servers and, ideally, remove them from internet exposure.
As attackers demonstrate the capability to execute stealthy attacks using CVE-2023-46604, this cautionary advice becomes paramount to mitigating the risks associated with this exploit and safeguarding systems from potential compromise.