Arbitrary user-submitted OGNL possible when using JSP EL or FreeMarker
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Key: WW-2107
URL: https://issues.apache.org/struts/browse/WW-2107
Project: Struts 2
Issue Type: Bug
Components: Views
Affects Versions: 2.0.9
Reporter: Don Brown
Priority: Blocker
Fix For: 2.0.10
It is possible for a user to submit malicious OGNL that could be executed in a
page that uses JSP EL expressions in Struts tag attributes. FreeMarker pages
that use FreeMarker expressions in Struts tag attributes are also affected.
For example, say you had this JSP page fragement:
<s:text name="foo" value="${bar}" />
And a user submitted, via a validation error or request url query parameter,
the value:
bar=%{1+1}
What happens is the JSP processor gets the page first and processes the JSP EL
expression resulting in:
<s:text name="foo" value="%{1+1}" />
Then, the Struts 2 tag receives the 'value' attribute value and processes the
OGNL expression, resulting in this:
<input type="text" name="foo" value="2" />
The workaround is to ensure you don't use JSP EL or FreeMarker expressions in
Struts tag attributes because you could be unwittingly allowing arbitrary code
execution.
The proposed solution is to turn off, via the TLD, JSP EL expressions in all
Struts tag attributes. This will mostly likely break many Struts 2
applications, but the severity of the issue needs to be taken into account.
This solution doesn't unfortunately resolve the FreeMarker issue.
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