If you are on APEX 4.2.2, you apply patch 4.2.3 to fix problems.
There is nothing to migrate in this case because APEX schema do not change.
So it means that i should download apex_4.2.3 files installation to migrate to apex 4.2.3 ?
No, it means you should download the p17347169_423_Generic.zip patch set from MOS using your Oracle Support identifier. Users without Oracle Support cannot patch a 4.2.x installation.
Upgrading a 4.2.x installation to 4.2.3 using the full apex_4.2.3.zip OTN download requires all workspaces and applications to be backed up, APEX 4.2.x to be uninstalled, performing a clean 4.2.3 installation, and restoring the backed up metadata.
Do you have an Oracle Support contract?