Thanks for your suggestion; it didn't solve the problem though.

 xbps-install -Su ca-certificates
[*] Updating `http://repo.voidlinux.eu/current/x86_64-repodata' ...
[*] Updating `http://repo.voidlinux.eu/current/multilib/nonfree/x86_64-repodata' ...
[*] Updating `http://repo.voidlinux.eu/current/multilib/x86_64-repodata' ...
[*] Updating `http://repo.voidlinux.eu/current/nonfree/x86_64-repodata' ...
libtls6-2.2.3_1 broken, needs `libcrypto35-2.2.4_3'
libtls6-2.2.3_1 broken, needs `libssl35-2.2.4_3'
Transaction aborted due to unresolved dependencies.

How to solve?