Have you heard of CVE-2022-39346? If you are using Nextcloud Server, this vulnerability could put the stability of your server at risk. In this long read, we will explore the details of this vulnerability affecting Nextcloud server versions before 22.2.10, 23..7, and 24..3, explain the exploit scenario, and provide recommendations on how to mitigate the issue. You should definitely follow us through to ensure your Nextcloud Server is safe!

What is the CVE-2022-39346 vulnerability?

Security researchers identified a vulnerability in Nextcloud Server that allows an attacker to potentially cause a denial of service (DoS) by overloading the database with excessively long user display names. Due to a lack of proper limitation on user display names, attackers can create and use accounts with unusually long display names to exploit this vulnerability, hampering the system's performance and availability. The vulnerability affects Nextcloud server versions before 22.2.10, 23..7, and 24..3.

How does the exploit work?

Let's assume the attacker registered an account on the server with a malicious display name. When the server's backing database attempts to store or retrieve the display name, it consumes an excessive amount of resources due to its length, resulting in sluggish performance and potentially crashing the database system. Here is a simple demonstration of an excessively long display name:

$displayName = str_repeat('A', 100000); // Create a string with 1,000,000 'A' characters
$user->setDisplayName($displayName); // Set the display name of the user to the long string

What is the impact of this vulnerability?

The severity of this vulnerability primarily depends on the server's ability to handle excessive data and the size of the database. If exploited successfully, the CVE-2022-39346 vulnerability can lead to disconnection issues, slow response times, and even full outages of the Nextcloud Server. This can negatively impact your Nextcloud-powered personal cloud server, which might carry essential files and confidential information.

How to fix the CVE-2022-39346 vulnerability?

The best solution for this vulnerability is upgrading your Nextcloud Server to the latest versions, as follows:

If you are using Nextcloud Server 23.x, upgrade to 24..3.

To upgrade your Nextcloud Server, follow the instructions in this official Nextcloud guide: Upgrading Nextcloud

Please note that there are no known workarounds for this issue. Protecting your Nextcloud Server is of utmost importance, so we strongly recommend applying upgrades as soon as possible.


CVE-2022-39346 is a denial of service vulnerability in Nextcloud Server that, if exploited, can potentially bring down your personal cloud server by overloading the database with exceedingly long user display names. If you are using affected versions of Nextcloud Server, upgrading your installation is crucial to ensure the security and stability of your server. Stay vigilant, and keep your Nextcloud Server up-to-date to minimize any potential impact on your personal or organizational data.


Published on: 11/25/2022 19:15:00 UTC
Last modified on: 12/13/2022 02:24:00 UTC