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  • S2-046
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Summary

Possible RCE when performing file upload based on Jakarta Multipart parser (similar to S2-045)

Who should read this

All Struts 2 developers and users

Impact of vulnerability

Possible RCE when performing file upload based on Jakarta Multipart parser

Maximum security rating

Critical

Recommendation

Upgrade to Struts 2.3.32 or Struts 2.5.10.1

Affected Software

Struts 2.3.5 - Struts 2.3.31, Struts 2.5 - Struts 2.5.10

Reporter

Chris Frohoff <cfrohoff at qualcomm dot com>, Nike Zheng <nike dot zheng at dbappsecurity dot com dot cn>, Alvaro Munoz <alvaro dot munoz at hpe dot com>

CVE Identifier

CVE-2017-5638

Problem

It is possible to perform a RCE attack with a malicious Content-Disposition value or with improper Content-Length header. If the Content-Dispostion / Content-Length value is not valid an exception is thrown which is then used to display an error message to a user. This is a different vector for the same vulnerability described in S2-045 (CVE-2017-5638).

Solution

If you are using Jakarta based file upload Multipart parser, upgrade to Apache Struts version 2.3.32 or 2.5.10.1.

Backward compatibility

No backward incompatibility issues are expected.

Workaround

You can switch to a different implementation of the Multipart parser. We have already prepared two plugins which can be used as a drop-in solution, please find them here. You can use them when you are running the Apache Struts 2.3.8 - 2.5.5 (in case of using the default Jakarta multipart parser) or the Apache Struts 2.3.20 - 2.5.5 (when using an alternative jakarta-stream multipart parser).

Another option is to remove the File Upload Interceptor from the stack, just define your own custom stack and set it as a default - please read How do we configure an Interceptor to be used with every Action. This will work only for Struts 2.5.8 - 2.5.10.

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