LimeSurvey is an open source and commercial web application that enables its users to quickly design and setup scalable surveys. We detected two vulnerabilities in LimeSurvey < 2.72.3: An unauthenticated persistent cross-site scripting vulnerability (CVE-2017-18358) and an authenticated arbitrary file write vulnerability which can be chained.
The exploitation of this vulnerability is only possible if the attacker can read, update and import templates. The attacker imports a new template by uploading a zip file containing a single
config.xml file. The XML file specifies the path of the file to be modified:
In this particular example the attacker modifies the
index.php file of the LimeSurvey web root by using the built-in template file editor. This is possible because the web application does not properly sanitize the filenames which are passed within the
<files_editable> tag. Therefore a path traversal attack will mislead the application logic to treat the
index.php of the web root as an editable file of the template. The following method
templatesave_changes() is invoked when processing modifications to the template through the built-in template editor.
On line 610 the new content of the file is received through the parameter
changes. The variable
$editfile holds the name of the file and is received on line 616. The if statement ranging from line 622 to line 624 is the only check to prevent an attacker from changing files which are not part of the template. By previously importing the malicious template, the array
$cssfiles will contain the file
index.php causing the check to complete successfully and the file is finally opened and written to on line 633 and 637 respectively.
|2017/11/08||Provided vulnerability details and PoC to vendor|
|2017/11/08||Vendor acknowledged and fixes cross-site scripting|
|2017/11/10||Fixed version released|