Can you explain this vulnerability to me?

CVE-2026-34821 is a stored cross-site scripting (XSS) vulnerability in Endian Firewall versions 3.3.25 and earlier. It occurs because the application does not properly neutralize input in the "remark" parameter of the /manage/vpnauthentication/user/ endpoint.

An authenticated attacker can inject arbitrary JavaScript code via this parameter, which is then stored on the server. When other users view the affected page, the malicious script executes in their browsers.

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How can this vulnerability impact me? :

This vulnerability allows an authenticated attacker to execute arbitrary JavaScript code in the browsers of other users who view the affected page. This can lead to unauthorized actions performed on behalf of those users, theft of sensitive information such as session tokens, or other malicious activities.

The CVSS v4 base score of 5.1 indicates a medium severity with low attack complexity and no requirement for user interaction beyond authentication.

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How can this vulnerability be detected on my network or system? Can you suggest some commands?

This vulnerability involves stored cross-site scripting (XSS) via the remark parameter in the /manage/vpnauthentication/user/ endpoint of Endian Firewall versions 3.3.25 and earlier.

To detect this vulnerability on your system, you can check if your Endian Firewall version is 3.3.25 or earlier, as these versions are affected.

Additionally, you can monitor HTTP requests to the /manage/vpnauthentication/user/ endpoint for suspicious input in the remark parameter that includes JavaScript code.

Suggested commands include using network traffic inspection tools like curl or wget to send authenticated requests and observe responses, or using web vulnerability scanners that support detection of stored XSS vulnerabilities.

• Example curl command to test the remark parameter (authentication required):
• curl -k -u <username>:<password> -X POST https://<firewall-ip>/manage/vpnauthentication/user/ -d "remark=<script>alert('XSS')</script>"
• Review the response or subsequent page loads to see if the injected script executes.

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What immediate steps should I take to mitigate this vulnerability?

The primary mitigation step is to update Endian Firewall to a version later than 3.3.25, as the vulnerability is fixed in newer versions.

Until an update can be applied, restrict access to the /manage/vpnauthentication/user/ endpoint to trusted authenticated users only.

Implement input validation or sanitization on the remark parameter to prevent injection of arbitrary JavaScript code.

Monitor logs and user activity for suspicious behavior that may indicate exploitation attempts.

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How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:

The vulnerability is a stored cross-site scripting (XSS) issue that allows an authenticated attacker to inject and execute arbitrary JavaScript code when other users view the affected page.

While the CVE description and resources do not explicitly mention compliance with standards such as GDPR or HIPAA, stored XSS vulnerabilities can potentially lead to unauthorized access or exposure of sensitive information, which may impact compliance with data protection regulations.

Organizations using affected versions of Endian Firewall should consider this vulnerability as a risk to confidentiality and integrity of user data, and address it promptly to maintain compliance with relevant security and privacy standards.

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