If you're using Linphone the /usr/local/share/linphone/rootca.pem needs updating.
Go to
https://wiki.mozilla.org/CA/Included_Certificates
pull down the text file

PEM of Root Certificates in Mozilla's Root Store with the Websites (TLS/SSL) Trust Bit Enabled (TXT)

Rename it rootca.pem
Move it to the /usr/local/share/linphone folder.