Unvalidated parent-supplied AWS Region in AWS aws-nitro-enclaves-sdk-c allows impersonation of the enclave's AWS KMS endpoint

Incomplete string validation in AWS aws-nitro-enclaves-sdk-c before 0.4.6 may allow a third party to impersonate the AWS KMS endpoint. To remediate this issue, users should rebuild any custom enclave image against aws-nitro-enclaves-sdk-c 0.4.6.