CVE-2021-22879: 
Nextcloud Desktop Client vulnerability analysis and mitigation

CVE-2021-22879 affects Nextcloud Desktop Client versions prior to 3.1.3. The vulnerability is related to missing validation of URLs, which could allow a malicious server to execute remote commands. The vulnerability was discovered in early 2021 and was publicly disclosed on April 14, 2021 (NVD, Gentoo Security).

The vulnerability stems from insufficient URL validation in the Nextcloud Desktop Client. The application failed to properly validate URLs coming from the server or user input, which could lead to resource injection. The issue was addressed by implementing validation that only allows http(s) schemes for sensitive URLs (GitHub PR). The vulnerability has a CVSS score of 7.0, indicating moderate severity (Rapid7).

If exploited, this vulnerability could allow a malicious server to execute remote commands on the user's system with the privileges of the user running the Nextcloud Desktop Client application. However, user interaction is required for successful exploitation (NVD, Gentoo Security).

The vulnerability requires user interaction for successful exploitation. An attacker would need to entice a user to connect to a malicious Nextcloud server to execute arbitrary commands (Gentoo Security).

The vulnerability was fixed in Nextcloud Desktop Client version 3.1.3. Users are advised to upgrade to this version or later. For Gentoo Linux users, the fix can be applied by running 'emerge --sync' followed by 'emerge --ask --oneshot --verbose ">=net-misc/nextcloud-client-3.1.3"' (Gentoo Security).