Error on validating CSR with "critical" in subjectAlternativeName

[medranocalvo]

Generate a CSR that marks the extension as critical:

openssl req -new -sha256 -key domain.key -subj "/" \
 -reqexts SAN -config <(cat /etc/ssl/openssl.cnf \
 <(printf "[SAN]\nsubjectAltName=critical,DNS:foo.com,DNS:www.foo.com"))

When pressing "Validate CSR", the following error appears:

Error: Failed validating CSR

Please, see https://www.openssl.org/docs/manmaster/apps/x509v3_config.html