Use-after-free in the SetClient command handler of kmstool-enclave in AWS aws-nitro-enclaves-sdk-c

A use-after-free and double-free issue in the SetClient command handler of the kmstool-enclave sample application of AWS aws-nitro-enclaves-sdk-c before 0.4.6 may allow an application that runs on the parent EC2 instance to corrupt heap memory inside a Nitro Enclave which may lead to arbitrary code execution within the enclave.

To remediate this issue, users should rebuild any enclave image that includes kmstool-enclave, or code derived from it, against aws-nitro-enclaves-sdk-c 0.4.6.