GHSA-rp9h-rf7g-hwgr: s2n-tls has undefined behavior at process exit

s2n-tls uses the Linux atexit function to register functions that clean up the global state when the process exits. In multi-threaded environments, the atexit handler may clean up state which is still in use by other threads. When this occurs, the exiting process may experience a segmentation fault or other undefined behavior.

Customers of AWS services do not need to take action. Applications using s2n-tls should upgrade to the most recent release of s2n-tls.

Impacted versions: < v1.5.9.