CVE-2021-39221 XSS in Contacts

Medium 6.4 Published 25 Oct 2021 Updated 4 Aug 2024

Stored XSS in Nextcloud Contacts allows attackers to execute scripts if users open malicious files in new tabs, mitigated by CSP on modern browsers.

Exploited in the wild: Not known
Login needed: Any signed-in user
Attackable: Over the internet
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2021-39221?

CVE-2021-39221 is a medium-severity cross-site scripting vulnerability in nextcloud security-advisories, published on 25 Oct 2021. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

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.

Weakness: CWE-79, CWE-434

Which versions are affected by CVE-2021-39221?

It affects 1 product.

Products include Nextcloud Contacts.

How do I fix CVE-2021-39221?

No fix has been published for CVE-2021-39221 yet. Limit exposure of the affected software until one is available.

Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.

Is CVE-2021-39221 being exploited?

There is no known exploitation of CVE-2021-39221 in the wild and no public exploit code.

Sources

Also known as GHSA-j6cx-mxqf-f9vc.