CVE-2020-1938 Ghostcat - Apache Tomcat AJP File Read/Inclusion

Virsec Security Research Lab Vulnerability Analysis

The Virsec Security Research Lab provides a detailed analysis of recent and notable security vulnerabilities.

1.1        Vulnerability Summary

When using the Apache JServ Protocol (AJP), care must be taken when trusting incoming connections to Apache Tomcat. Tomcat treats AJP connections as having higher trust than, for example, a similar HTTP connection. If such connections are available to an attacker, they can be exploited in ways that may be surprising. In Apache Tomcat 9.0.0.M1 to, 8.5.0 to 8.5.50 and 7.0.0 to 7.0.99, Tomcat shipped with an AJP Connector enabled by default that listened on all configured IP addresses. It was expected (and recommended in the security guide) that this Connector would be disabled if not required. This vulnerability report identified a mechanism that allowed: - returning arbitrary files from anywhere in the web application - processing any file in the web application as a JSP. Further, if the web application allowed file upload and stored those files within the web application (or the attacker was able to control the content of the web application by some other means) then this, along with the ability to process a file as a JSP, made remote code execution possible.

It is important to note that mitigation is only required if an AJP port is accessible to untrusted users. Users wishing to take a defense-in-depth approach and block the vector that permits returning arbitrary files and execution as JSP may upgrade to Apache Tomcat 9.0.31, 8.5.51 or 7.0.100 or later. A few changes were made to the default AJP Connector configuration in 9.0.31 to harden the default configuration. It is likely that users upgrading to 9.0.31, 8.5.51 or 7.0.100 or later will need to make small changes to their configurations.

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1.2        CVSS Score

The CVSS Base Score is 9.8 (Critical)

1.3        Affected Version

Apache Tomcat 9.0.30 and prior, Apache Tomcat 8.5.50 and prior and Apache Tomcat 7.0.99 and prior.

Vulnerability Attribution

This vulnerability was discovered by a security researcher of Chaitin Tech. Henry Chen, a security researcher at Alibaba Cloud, published a tweet confirming that exploiting the vulnerability would allow someone to “read any WebApps files or include a file to RCE.”

Risk Impact

According to a tweet by cyber threat intelligence firm Bad Packets, “mass scanning activity targeting this vulnerability has already begun”. It can be used to read configs and steal passwords & API tokens - In some cases, it can be used to RCE/write files (think "plant backdoors") with at least 5 POCs already available.

Based on this link from 2010, Apache Tomcat has been downloaded 10 Million times. Tomcat has 60% market share of Java Application servers. Given that Apache Tomcat powers a broad range of web applications across countless industries and use cases, from Fortune 500 conglomerates to service providers to eCommerce systems, it is reasonable to estimate that 10s of millions of this software are in use.

Virsec Security Platform (VSP) Support

VSP-Web LFI capability can detect such an attack from being exploited. VSP-Host monitors processes that are spawned which are not part of a set of whitelisted processes. Any attempt to execute new command or unknown binary would be denied by VSP-Host’s Process Monitoring capability. VSP-Host FSM capability would also detect the attempt to place a web shell on disk.

Reference Links:

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About the Author
Satya Gupta is Virsec’s visionary founder, with over 25 years of expertise in embedded systems, network security and systems architecture. Satya has helped build and guide the company through key growth phases from initial funding (2015), developing core technology with key partners including Raytheon and Lockheed (2016-2018), to launching an enterprise class, GA product (2019). Prior to this, Satya built a highly profitable software design and consulting business targeting data networking, application security and industrial automation projects. He was also Director of Firmware Engineering at Narad Networks and Managing Director and Chief Engineer at Eastern Telecom and Tech Ltd. Satya has more than 40 patents in complex firmware architecture with products deployed to hundreds of thousands of users. He holds a BS degree in Engineering from the Indian Institute of Technology in Kanpur and additional degrees from the University of Massachusetts at Lowell.