What Regex does Openvas use for validating CIDR

I am getting “Error in host specification” error many of time for CIDRs such as

when I am validating these online with IP calculators, it is showing as valid.
Please help me with the library that Openvas use for validating CIDRs or Subnets

Closing as a duplicate of How to scan an entire subnet as this is most likely a GMP issue already discussed there.