build project environment image override

One easy way of testing this is to open your CodeBuild project and to perform a build with overrides (see "Start build with overrides" button). Here, select "Advanced build overrides" to gain access to the option to modify the environment image. Select "Override image" and chose the new image that you want to test your build with, for example "aws/codebuild/standard:6.0" if you want to update from Ubuntu 18.04 (standard 4:0) to Ubuntu 22.04, which is the latest Ubuntu image provided by CodeBuild as of this date. Confirm the selection with "Start build" and verify via the build status and logs.

If everything went fine, you can safely update the build project permanently with the successfully tested image. Depending on whether you're using an "Infrastructure as Code" approach such as CloudFormation, CDK or Terraform, you'll either have to update the image within the corresponding code, or you apply the changes via the AWS Console ("Edit" > "Environment" > "Override image").

Hope this helps!