Subversion's mod_authz_svn module will crash if the server is using in-repository authz rules with the AuthzSVNReposRelativeAccessFile option and a client sends a request for a non-existing repository URL. This can lead to disruption for users of the service. This issue was fixed in mod_dav_svn+mod_authz_svn servers 1.14.1 and mod_dav_svn+mod_authz_svn servers 1.10.7
https://subversion.apache.org/security/CVE-2020-17525-advisory.txt
https://lists.debian.org/debian-lts-announce/2021/05/msg00000.html