CVE-2021-39222 : Vulnerability Insights and Analysis

Nextcloud is an open-source, self-hosted productivity platform. The Nextcloud Talk application was vulnerable to a stored Cross-Site Scripting (XSS) vulnerability.

Understanding CVE-2021-39222

Nextcloud Talk application has a vulnerability that could lead to the execution of malicious scripts when interacting with specially crafted files.

What is CVE-2021-39222?

The XSS vulnerability in Nextcloud Talk could allow an attacker to execute arbitrary code by tricking a user into interacting with a malicious file.

The Impact of CVE-2021-39222

This vulnerability has a CVSS base score of 6.4 (Medium severity) and could lead to compromised confidentiality and integrity.

Technical Details of CVE-2021-39222

The technical details of this CVE provide insight into the vulnerability's nature, affected systems, and exploitation mechanisms.

Vulnerability Description

CWE-434: Unrestricted Upload of File with Dangerous Type
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Affected Systems and Versions

Versions prior to 10.0.7
Versions >= 10.1.0, < 10.1.4
Versions >= 11.1.0, < 11.1.2
Versions < 11.2.0
Versions >= 12.0.0.alpha-1, < 12.0.0

Exploitation Mechanism

To exploit this vulnerability, a user would need to right-click on a malicious file within the Nextcloud Talk application and open it in a new tab.

Mitigation and Prevention

Protecting systems from CVE-2021-39222 requires immediate actions and long-term security measures.

Immediate Steps to Take

Upgrade Nextcloud Talk application to patched versions (10.0.7, 10.1.4, 11.1.2, 11.2.0, or 12.0.0)
Use a browser supporting Content-Security-Policy

Long-Term Security Practices

Implement strict Content-Security-Policy settings
Educate users on safe browsing habits and file interactions

Patching and Updates

Regularly check for security advisories and updates from Nextcloud to ensure software is up-to-date and secure.