Attacker Value
High
(4 users assessed)
Exploitability
Very High
(4 users assessed)
User Interaction
None
Privileges Required
None
Attack Vector
Network
0

CVE-2020-1938

Disclosure Date: February 24, 2020
Add any MITRE ATT&CK Tactics to the list below that apply to this CVE.

Description

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.

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4
Ratings
Technical Analysis

Current PoC’s offer unauthenticated LFI inside the webroot.
Depending on the application and organisations configuration this could reveal sensitive information from database config or other configurations within the source code.

There is the potential for RFI / RCE although example of this are not yet public.

With a shift towards containers like Kubernetes / Docker it is important to note that older tags which may be version pinned by organisations are unlikely to be patched.

The official containers distributed by Apache include tags for vulnerable version although they do not appear to server port 8009 by default. A custom server.xml is required. This is “Likely” to happen.

3
Ratings
  • Attacker Value
    High
  • Exploitability
    Very High
Technical Analysis

Just a quick note the Tenable blog has a number of useful resources here, which also links to a few other PoC scripts:

https://www.tenable.com/blog/cve-2020-1938-ghostcat-apache-tomcat-ajp-file-readinclusion-vulnerability-cnvd-2020-10487

2
Ratings
Technical Analysis

after having spent some time trying to traverse webroot, i feel like saying that it’s “unlikely” that ajp will let you read file through the filesystem, because of how tomcat segregates the environment.
i’d love being proven wrong.

having file upload on the docroot, as other said, it’s possible to achieve RCE quite easily.
(un)fortunately, the file can be anything, even a valid image with the classic code-append like we all did in php. given this behaviour, it’s trivial to bypass upload filters.

2
Ratings
Technical Analysis

We’re still trying to find a way to get generic RCE out of this, but it’s not promising: https://twitter.com/steventseeley/status/1230871514343518208. For now, it seems to be limited to LFI in the web root.

I did manage to get a shell, but it was rather contrived, since I uploaded the text file containing JSP myself, then included it. It at least did not require a .jsp extension, but the extension was required in the request URI.

General Information

Vendors

  • Apache

Products

  • Apache Tomcat

References

Advisory

Additional Info

Technical Analysis