Unauthorized Error with AWS EKS Authentication in CI/CD Pipeline Despite Valid Kubeconfig

I'm facing authentication issues when trying to access an AWS EKS cluster through kubectl in a CI/CD pipeline environment, even though the same configuration works locally. Specifically, I'm encountering an "Unauthorized" error after executing the aws eks update-kubeconfig command.

Details:

The KUBECONFIG file appears to be properly set up and contains valid authentication information, which works on my local machine.

I'm using an IAM role with admin access in the CI/CD environment, which should provide the correct permissions, and I’ve verified the necessary IAM policies (eks:DescribeCluster, eks:UpdateKubeconfig, etc.) are attached.

Despite this, when running kubectl commands in the CI/CD pipeline, I receive an "Unauthorized" error, implying issues with the token authentication or the environment’s role assumption.

Steps Taken:

Verified that the aws eks update-kubeconfig command outputs the correct KUBECONFIG and authentication data.

Attempted to validate the IAM role assumption (aws sts get-caller-identity) and ensured it has the proper permissions.

Checked the aws CLI configuration in the CI/CD environment to confirm the correct credentials and region. ** Questions:**

Could there be an issue with how the IAM role is assumed in the CI/CD pipeline? How can I ensure the correct role assumption?

Are there any additional permissions or role settings required for the CI/CD environment to authenticate properly with the EKS cluster?

How can I further troubleshoot the "Unauthorized" error to pinpoint the problem?