Nextcloud is an Open Source private cloud software. Versions 25.0.0 and above, prior to 25.0.3, are subject to Uncontrolled Resource Consumption. A user can configure a very long password, consuming more resources on password validation than desired. This issue is patched in 25.0.3 No workaround is available.
https://hackerone.com/reports/1820864
https://github.com/nextcloud/server/pull/35965
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-53q2-cm29-7j83