You attempt to install Red Hat updates using yum, and you receive an error similar to the following:
up2date_client.up2dateErrors.SSLCertificateVerifyFailedError: The certificate is expired. Please ensure you have the correct certificate and your system time is correct.
Remove the expired certificate and replace it with the new certificate:
rm /usr/share/rhn/RHNS-CA-CERT wget -P /usr/share/rhn http://f.cl.ly/items/1B19031O2E0m1k3E2n3u/RHNS-CA-CERT
Update the Red Hat Network packages:
yum -y update rhn*
Red Hat’s old certificate expired in August 2013, so any server that hadn’t installed updated since the new certificate was provided in March 2010 won’t be able to validate the new packages. For more information, see this article on Red Hat’s KB.
To prevent issues like this from occurring in the future, please install Red Hat updates at least two times per year.