The CC license only covers Licensed Rights that the Licensor owns or is authorized to grant to the user. It does not come with a guarantee (or warranty) that the user has all the rights necessary to use the material. So no, third-party copyrights are not covered by the license.
However, Creative Commons (the organization) recommends that:
Licensors should also secure all rights necessary before applying our licenses so that the public can reuse the material as expected. Licensors should clearly mark any material not subject to the license. This includes other CC-licensed material, or material used under an exception or limitation to copyright.
The CC license only covers Licensed Rights that the Licensor owns or is authorized to grant to the user. It does not come with a guarantee (or warranty) that the user has all the rights necessary to use the material. So no, third-party copyrights are not covered by the license.
However, Creative Commons (the organization) recommends that: