ULN is moving towards the DigiCert G2 root certificate. The change in server certificates on ULN will occur on April 14th, 2026.  
Due to the nature of how Oracle Linux systems connect to Unbreakable Linux Network (ULN), this change requires that client 
certificates on all Oracle Linux systems receiving updates from ULN be updated before April 14th, 2026. After this time, 
Oracle Linux systems will only be able to connect to ULN Service with an updated client certificate. 

To replace the client SSL certificate on an Oracle Linux machine, run the following steps as root on each server:

 # cp /usr/share/rhn/ULN-CA-CERT /usr/share/rhn/ULN-CA-CERT.old
 # wget https://linux-update.oracle.com/rpms/ULN-CA-CERT.digig2
 # cp ULN-CA-CERT.digig2 /usr/share/rhn/ULN-CA-CERT

After you apply the update, run the command below to verify the new SSL certificate contains Root G2 issuer:

# grep "DigiCert Global Root G2" /usr/share/rhn/ULN-CA-CERT

        Issuer: C=US, O=DigiCert Inc, OU=www.digicert.com, CN=DigiCert Global Root G2

        Subject: C=US, O=DigiCert Inc, OU=www.digicert.com, CN=DigiCert Global Root G2


Possible issues seen if ULN-CA-CERT certificate is not updated at client:

1. uln_register command won't proceed to the next screen

2.  ulnreg_ks command fails with below error

# ulnreg_ks --username=<username> --password=<password> --csi=<csi> 
An error has occurred:
The SSL certificate failed verification.
See /var/log/up2date for more information

3. dnf/yum command fails with SSL certificate error

# dnf update
Error: The SSL certificate failed verification.