GHSA-534C-HCR7-67JG

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.

Local File Read / RCE in edge cases where phar:// can be utilized with gadget chains .

export.xlsx
sample_template.xlsx

An XML parser processes external entity references in untrusted input, causing the server to fetch internal resources or remote URLs. Typical impact: local file disclosure, server-side request forgery, or denial of service.

GHSA-534C-HCR7-67JG has a CVSS score of 6.5 (High). The vector is network-reachable, high privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (2.21.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is GHSA-534C-HCR7-67JG? GHSA-534C-HCR7-67JG is a high-severity XML external entity injection (XXE) vulnerability in kimai/kimai (composer), affecting versions <= 2.20.1. It is fixed in 2.21.0. An XML parser processes external entity references in untrusted input, causing the server to fetch internal resources or remote URLs.
2. How severe is GHSA-534C-HCR7-67JG? GHSA-534C-HCR7-67JG has a CVSS score of 6.5 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of kimai/kimai are affected by GHSA-534C-HCR7-67JG? kimai/kimai (composer) versions <= 2.20.1 is affected.
4. Is there a fix for GHSA-534C-HCR7-67JG? Yes. GHSA-534C-HCR7-67JG is fixed in 2.21.0. Upgrade to this version or later.
5. Is GHSA-534C-HCR7-67JG exploitable, and should I be worried? Whether GHSA-534C-HCR7-67JG is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-534C-HCR7-67JG is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-534C-HCR7-67JG? Upgrade kimai/kimai to 2.21.0 or later.

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