CVE-2023-38491 Explained : Impact and Mitigation

A Cross-site Scripting (XSS) vulnerability in Kirby content management system versions prior to 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, and 3.9.6 poses a risk to sites allowing file uploads, potentially leading to the execution of harmful scripts.

Understanding CVE-2023-38491

Kirby is vulnerable to Cross-site scripting (XSS) due to improper neutralization of input during web page generation, affecting certain versions prior to the patched releases.

What is CVE-2023-38491?

The vulnerability allows attackers to upload arbitary HTML files containing harmful content via Kirby Panel, potentially impacting authenticated users or external visitors interacting with the site.

The Impact of CVE-2023-38491

Users with write access could upload malicious files with unknown extensions, leading to script execution when accessed, potentially affecting API calls and site security.

Technical Details of CVE-2023-38491

The vulnerability stems from the

Kirby\Http\Response::file()

method's lack of explicit fallback for MIME types, allowing the execution of potentially harmful scripts.

Vulnerability Description

Attackers can exploit the vulnerability by uploading HTML files with unknown extensions, triggering script execution when accessed by authenticated users or visitors.

Affected Systems and Versions

Kirby versions prior to 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, and 3.9.6 are susceptible to the XSS vulnerability when allowing untrusted users or visitors to upload files.

Exploitation Mechanism

By uploading HTML files with unknown extensions, attackers can trick users into accessing harmful scripts, potentially compromising site security and triggering API requests.

Mitigation and Prevention

To safeguard against CVE-2023-38491, immediate actions include updating Kirby to the patched versions and implementing secure file upload policies.

Immediate Steps to Take

Ensure Kirby is updated to versions 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, or 3.9.6 to mitigate the XSS vulnerability and review file upload policies for untrusted users.

Long-Term Security Practices

Regularly monitor for security updates, restrict file extensions for uploads, and educate users on safe browsing practices to prevent XSS attacks.

Patching and Updates

Kirby addressed the vulnerability in versions 3.5.8.3, 3.6.6.3, 3.7.5.2, 3.8.4.1, and 3.9.6 by implementing a fallback MIME type of

text/plain

and enhancing file content type detection to mitigate XSS risks.