Authentication of SVN operations can be bypassed when the database field unix_pw is empty for a user. This can happen if:
- the setting homedir_prefix is empty
- the account of the user has been automatically created during its first login through a OpenIDConnect provider
- the account is created through the LDAP plugin and the user has never logged in the web UI and for some reasons the SVN repo does not rely on LDAP to deal with the authentication
Impact
An attacker could use this vulnerability to access and update SVN repositories he does not have access to.
CVSSv3 score: 8.2 (CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N)
Exploitation
Set an ampty string in the field unix_pw of the DB for one of your user. Any password will be accepted when doing SVN operations. Authorizations are still enforced so you need to use a user with enough access to at least read the repo.
References
CWE 287