Nextcloud server is an open source, self hosted cloud style services platform. In affected versions an attacker can cause a denial of service by uploading specially crafted files which will cause the server to allocate too much memory / CPU. It is recommended that the Nextcloud Server is upgraded to 21.0.8 , 22.2.4 or 23.0.1. Users unable to upgrade should disable preview generation with the `'enable_previews'` config flag.
https://security.gentoo.org/glsa/202208-17
https://hackerone.com/reports/1261225
https://github.com/nextcloud/server/pull/30291
https://github.com/nextcloud/security-advisories/security/advisories/GHSA-jf3h-xf4q-mh89