CVE-2021-39221: Nextcloud Contacts

Medium severity, CVSS 5.4. EPSS: 0.5% chance of exploitation in the next 30 days.

Nextcloud is an open-source, self-hosted productivity platform. The Nextcloud Contacts application prior to version 4.0.3 was vulnerable to a stored Cross-Site Scripting (XSS) vulnerability. For exploitation, a user would need to right-click on a malicious file and open the file in a new tab. Due the strict Content-Security-Policy shipped with Nextcloud, this issue is not exploitable on modern browsers supporting Content-Security-Policy. It is recommended that the Nextcloud Contacts application is upgraded to 4.0.3. As a workaround, one may use a browser that has support for Content-Security-Policy.

Affected products

• Nextcloud Contacts: before 4.0.3 (fixed in 4.0.3)

Published 2021-10-25. Last modified 2026-06-17.