Apache Struts Flaw Increasingly Exploited to Hack Servers

Security firm Imperva has detected thousands of attacks attempting to exploit a recently patched remote code execution vulnerability affecting the Apache Struts 2 open source development framework.

The security hole, tracked as CVE-2017-9805, affects applications that use the REST plugin with the XStream handler for XML payloads, and it exists due to the way Struts deserializes untrusted data. An exploit was made available within hours after a patch was released.

A few days later, Cisco Talos and Belgium-based NVISO Labs reported seeing exploitation attempts in the wild. However, a majority of the attacks only aimed to find vulnerable servers.

Imperva’s systems have blocked thousands of attacks, and the company says roughly 80% of them attempted to deliver a malicious payload, rather than just trying to determine if a server is vulnerable.

Roughly two-thirds of the attacks seen by the company involved Wget, a utility designed for downloading files. The list of payloads also included the /bin/sh system shell, the dig network administration tool, the cURL data transfer tool, and the certificate services program Certutil.

The biggest attack source was China, with a single Chinese IP sending out more than 40% of all the requests. The IP address in question is registered to a Chinese e-commerce company and experts believe the attackers may have compromised one of its devices. Attacks also came from Australia, the United States, Brazil, Canada, Russia and various European countries.

In many cases, cybercriminals executed commands to retrieve a malicious payload that would allow them to take control of the targeted server and abuse it for distributed denial-of-service (DDoS) and other attacks.

Cisco checking products for Apache Struts vulnerability

Several vulnerabilities have been patched in Apache Struts 2 this month and Cisco has started checking its products in order to determine which of them may be exposed to attacks.

While there are some products still under investigation, CVE-2017-9805 has so far been found to impact the company’s MXE 3500 Series Media Experience Engines, Unified Contact Center Enterprise, Unified Intelligent Contact Management Enterprise, and Network Performance Analysis.

A less severe remote code execution flaw patched in Apache Struts 2 last week, CVE-2017-12611, has been found to affect Cisco Digital Media Manager, Hosted Collaboration Solution for Contact Center, Unified Contact Center Enterprise, and Unified Intelligent Contact Management Enterprise.

Apache Struts flaw blamed for Equifax breach

According to some reports, the recent Equifax breach, which affects roughly 143 million consumers in the United States, involved an Apache Struts vulnerability.

While some have jumped to conclude that the flaw in question could be CVE-2017-9805, a more likely scenario is that attackers leveraged CVE-2017-5638, a vulnerability exploited in the wild since March. Equifax has yet to confirm that a Struts flaw was in fact used in the operation targeting its systems.