GHSA-hwcp-2h35-p66w is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in phpoffice/phpspreadsheet. A fix is available for phpoffice/phpspreadsheet — see the affected versions and patch details below.
PhpSpreadsheet has a Cross-Site Scripting (XSS) vulnerability of the hyperlink base in the HTML page header
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for GHSA-hwcp-2h35-p66w.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-hwcp-2h35-p66w by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 379,842 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpspreadsheet🐘phpoffice/phpexcelReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Cross-Site Scripting (XSS) vulnerability of the hyperlink base in the HTML page header
Product: Phpspreadsheet
Version: version 3.6.0
CWE-ID: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CVSS vector v.3.1: 5.4 (AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N)
CVSS vector v.4.0: 4.8 (AV:N/AC:L/AT:N/PR:L/UI:A/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N)
Description: the HTML page is formed without sanitizing the hyperlink base
Impact: executing arbitrary JavaScript code in the browser
Vulnerable component: class PhpOffice\PhpSpreadsheet\Writer\Html, method generateHTMLHeader
Exploitation conditions: a user viewing a specially generated Excel file
Mitigation: additional sanitization of special characters in a string
Researcher: Aleksey Solovev (Positive Technologies)
Research
The researcher discovered zero-day vulnerability Cross-Site Scripting (XSS) vulnerability of the hyperlink base in the HTML page header in Phpspreadsheet. The following code is written on the server, which translates the XLSX file into a HTML representation and displays it in the response.
Listing 8. Source code on the server
<?php
require __DIR__ . '/vendor/autoload.php';
$inputFileName = './doc/Book1.xlsx';
$spreadsheet = \PhpOffice\PhpSpreadsheet\IOFactory::load($inputFileName);
$writer = new \PhpOffice\PhpSpreadsheet\Writer\Html($spreadsheet);
print($writer->generateHTMLAll());
An attacker can embed a payload in a file property that will result in the execution of arbitrary JavaScript code.
The Excel file is unpacked and a HyperlinkBase in the file is inserted into the docProps/app.xml file.
Figure 14. Embedding the payload
After the changes were made, a new archive with the xlsx extension was created. At the moment of converting the xlsx file into the HTML representation, a property is obtained that participates in the formation of a string without sanitization.
Figure 15. Generating the HTML page header using the HyperlinkBase property
After generating and displaying the HTML representation of the XLSX file, arbitrary JavaScript code will be executed. <img width="356" alt="fig16" src="https://github.com/user-attachments/assets/c3694661-31e3-4be8-9a86-6eb4dd4647b5" />
Figure 16. Executing arbitrary JavaScript code
Credit
This vulnerability was discovered by Aleksey Solovev (Positive Technologies)
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | phpoffice/phpspreadsheet | ≥ 3.0.0&&< 3.7.0 | 3.7.0composer require phpoffice/phpspreadsheet:^3.7.0 |
| 🐘Packagist | phpoffice/phpspreadsheet | all versions | 1.29.7composer require phpoffice/phpspreadsheet:^1.29.7 |
| 🐘Packagist | phpoffice/phpspreadsheet | ≥ 2.0.0&&< 2.1.6 | 2.1.6composer require phpoffice/phpspreadsheet:^2.1.6 |
| 🐘Packagist | phpoffice/phpspreadsheet | ≥ 2.2.0&&< 2.3.5 | 2.3.5composer require phpoffice/phpspreadsheet:^2.3.5 |
| 🐘Packagist | phpoffice/phpexcel | all versions | No fix |
Affected Products
phpspreadsheetphpofficeDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for phpoffice/phpspreadsheet, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update phpoffice/phpspreadsheet to 3.7.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-hwcp-2h35-p66w is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is GHSA-hwcp-2h35-p66w in your dependencies?
Find it across Packagist, including transitive dependencies.