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GhostCat Request Injection Vulnerability

The Apache Software Foundation has released details of an improper input validation (CWE-20) vulnerability, known as GhostCat, affecting the Tomcat Java web server. They claim that an unauthenticated remote user could exploit this vulnerability to gain control of an affected system.

Threat ID:
CC-3384
Category:
Exploit
Threat Severity:
Medium
Threat Vector:
Insecure network
Published:
4 March 2020 12:00 AM
Report a cyber attack: call 0300 303 5222 or email [email protected]

Summary

The Apache Software Foundation has released details of an improper input validation (CWE-20) vulnerability, known as GhostCat, affecting the Tomcat Java web server. They claim that an unauthenticated remote user could exploit this vulnerability to gain control of an affected system.

Affected platforms

The following platforms are known to be affected:

Versions: 9.x prior to 9.0.31, 8.x prior to 8.5.51, and 7.x prior to 7.0.100

Apache Tomcat

Threat details

Description

The vulnerability is a result of the way Tomcat servers handle AJP connections. All prior versions of Tomcat used an AJP connector that was enabled by default.

Apache JServ Protocol

Apache JServ Protocol (AJP) is a packet-oriented binary protocol designed to proxy inbound requests from a public web server to a private application server. AJP reduces the performance overhead required to parse plain-text protocol, such as HTTP, and is primarily used for load balancing.

As AJP connections are typically between front-end and back-end systems, they are assigned higher trust ratings than connections using other protocols. AJP connections shoudl only be used via private interfaces.

If an AJP connection is exposed publicly, any unauthenticated user with access to it may make requests to the application server. An attacker can use this to bypass security and authentication measures, obtain sensitive information, or pass files to the server and execute them.

Remediation advice

The ASF has confirmed that CVE-2020-1938 has been addressed in the latest versions of Tomcat. Affected organisations are encouraged to visit the following pages to obtain and apply these updates:

They have also recommended organisations apply the following mitigation steps alongside any relevant updates:

  • Disabling the AJP connector and blocking TCP port 8009 if AJP support is not required.
  • If AJP support is required:
    • configure appropriate firewall rules
    • configure n explicit address attributed to ensure the AJP connector listens on private interface
    • configure a shared secret for the APJ connector

CVE Vulnerabilities

Status Master

CVE-2020-1938

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 9.0.0.30, 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 defence-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 number of 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.

Last edited: 4 March 2020 1:40 pm