CVE-2021-41177: Nextcloud Server

High severity, CVSS 8.1. EPSS: 1.6% chance of exploitation in the next 30 days.

Nextcloud is an open-source, self-hosted productivity platform. Prior to versions 20.0.13, 21.0.5, and 22.2.0, Nextcloud Server did not implement a database backend for rate-limiting purposes. Any component of Nextcloud using rate-limits (as as `AnonRateThrottle` or `UserRateThrottle`) was thus not rate limited on instances not having a memory cache backend configured. In the case of a default installation, this would notably include the rate-limits on the two factor codes. It is recommended that the Nextcloud Server be upgraded to 20.0.13, 21.0.5, or 22.2.0. As a workaround, enable a memory cache backend in `config.php`.

Affected products

• Nextcloud Nextcloud Server: before 20.0.13 (fixed in 20.0.13); from 21.0.0, before 21.0.5 (fixed in 21.0.5); from 22.0.0, before 22.2.0 (fixed in 22.2.0)

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