Summary
Kimai uses PHPSpreadsheet for importing and exporting invoices. Recently, a CVE was identified in PHPSpreadsheet, which could lead to an XXE vulnerability.
Details
Exploitation requires an Administrator account, allowing the upload of an XLSX template containing the payload. The vulnerability is triggered by the following code snippet:
// https://github.com/kimai/kimai/blob/b1903ba18359be16dd32ea9c40377c486498f082/src/Invoice/Renderer/AbstractSpreadsheetRenderer.php#L41
public function render(InvoiceDocument $document, InvoiceModel $model): Response
{
$spreadsheet = IOFactory::load($document->getFilename());
$worksheet = $spreadsheet->getActiveSheet();
$entries = $model->getCalculator()->getEntries();
$sheetReplacer = $model->toArray();
$invoiceItemCount = \count($entries);
if ($invoiceItemCount > 1) {
$this->addTemplateRows($worksheet, $invoiceItemCount);
}
}The IOFactory::load function utilizes simplexml_load_string, which has previously been demonstrated to be vulnerable to XXE attacks.
While this is not directly an XXE in Kimai, it does however impact the latest stable version.
PoC
By uploading a malicious XLSX template, the payload will be triggered every time an invoice is generated.
<?xml version="1.0" encoding='UTF-7' standalone="yes"?>
+ADw-!DOCTYPE foo [ <!ENTITY % xxe SYSTEM "php://filter/......." > %xxe;]>.....
For a better a visibility, I will upload both a:
- Malicious template sample for testing
- An exported invoice, showing the contents of target file during the export.
Impact
Local File Read / RCE in edge cases where phar:// can be utilized with gadget chains .
export.xlsx
sample_template.xlsx
References
ixSly Reporter
Summary
Kimai uses PHPSpreadsheet for importing and exporting invoices. Recently, a CVE was identified in PHPSpreadsheet, which could lead to an XXE vulnerability.
Details
Exploitation requires an Administrator account, allowing the upload of an
XLSXtemplate containing the payload. The vulnerability is triggered by the following code snippet:The
IOFactory::loadfunction utilizessimplexml_load_string, which has previously been demonstrated to be vulnerable to XXE attacks.While this is not directly an XXE in Kimai, it does however impact the latest stable version.
PoC
By uploading a malicious
XLSXtemplate, the payload will be triggered every time an invoice is generated.For a better a visibility, I will upload both a:
Impact
Local File Read / RCE in edge cases where
phar://can be utilized with gadget chains .export.xlsx
sample_template.xlsx
References