Single use execution environment with scoped credentials for on-demand code execution

Systems and methods are provided for scoped credentials within secure execution environments executing within virtual machines instances in an on-demand code execution system. In the on-demand code execution system, the execution environments are reset after every request or session. By resetting the single execution environment after each request or session, security issues are addressed, such as side-channel attacks and persistent malware. Additionally, the use of scoped credentials improves security by limiting the access rights for each code execution request or session to the smallest atomic level for the request or session. Following the request or session, the scoped credential is invalidated.