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changes.mady.by.user Lukasz Lenart

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Excerpt

Possible Remote Code Execution attack when using the Struts REST plugin with XStream handler to handle XML payloads


Who should read this

All Struts 2 developers and users

Impact of vulnerability

A RCE attack is possible when using the Struts REST plugin with XStream handler to deserialise XML requests

Maximum security rating

Critical

Recommendation

Upgrade to Struts 2.5.13 or Struts 2.3.34

Affected Software

Struts 2.1.

2

6 - Struts 2.3.33, Struts 2.5 - Struts 2.5.12

Reporter

Man Yue Mo <mmo at semmle dot com> (lgtm.com / Semmle). More information on the lgtm.com blog: https://lgtm.com/blog

CVE Identifier

CVE-2017-9805

Problem

The REST Plugin is using a XStreamHandler with an instance of XStream for deserialization without any type filtering and this can lead to Remote Code Execution when deserializing XML payloads.

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  1. Disable handling XML pages and requests to such pages

    Code Block
    xml
    xml
    <constant name="struts.action.extension" value="xhtml,,json" />


  2. Override getContentType in XStreamHandler

    Code Block
    languagejava
    public class MyXStreamHandler extends XStreamHandler { public String getContentType() {
 return "not-existing-content-type-@;/&%$#@";
 }
}


  3. Register the handler by overriding the one provided by the framework in your struts.xml

    Code Block
    xml
    xml
    <bean type="org.apache.struts2.rest.handler.ContentTypeHandler" name="myXStreamHandmer" class="com.company.MyXStreamHandler"/>
<constant name="struts.rest.handlerOverride.xml" value="myXStreamHandler"/>

 

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