This powershell script generates a new certificate, removes the old certificate assignments from the IISExpress ssl ports and adds the newly generated one. The certificate is also copied over to the Trusted Root Certificate Authorities.

UpdateIISExpressCertificate.ps1

$cert = New-SelfSignedCertificate -DnsName "localhost", "localhost" -CertStoreLocation "cert:\LocalMachine\My" -NotAfter (Get-Date).AddYears(5)
$thumb = $cert.GetCertHashString()

For ($i=44300; $i -le 44399; $i++) {
    netsh http delete sslcert ipport=0.0.0.0:$i
}

For ($i=44300; $i -le 44399; $i++) {
    netsh http add sslcert ipport=0.0.0.0:$i certhash=$thumb appid=`{214124cd-d05b-4309-9af9-9caa44b2b74a`}
}

$StoreScope = 'LocalMachine'
$StoreName = 'root'

$Store = New-Object  -TypeName System.Security.Cryptography.X509Certificates.X509Store  -ArgumentList $StoreName, $StoreScope
$Store.Open([System.Security.Cryptography.X509Certificates.OpenFlags]::ReadWrite)
$Store.Add($cert)

$Store.Close()

🙏 Thank you!

Had a legacy project to deal with and tripped over this, problem, your script worked like a charm. Found the gist via https://steffbeckers.eu/blog/iis-express-localhost-ssl-certificate-reset which also has a useful minimum test project at https://github.com/steffbeckers/iis-express-ssl-reset-test