While the Solaris OS is free, support comes at a cost. The exact policy is not very stable.
Currently, even to access the recommended patches you need a support contract. When a new Solaris update is released (roughly twice a year), it is freely downloadable and will include all recommended patches.
Only a limited number of patches are free (like patches to the patch tools). Since Sun was acquired by Oracle free access to security patches has stopped. Here are the links to see all Solaris patches since the last update (takes a while to load):
- For SPARC-based systems:
- For x86–based systems: