[arcfour]

Firecracker is extremely hardened, so I wouldn't worry about Lambda. As for ECS, getting root doesn't necessarily mean you have a container escape. I think you could escape containers with this exploit, but you would need a different payload than what's published. I could be wrong though.

I would assume AWS is pretty on the ball when it comes to handling stuff like this if they didn't have other defenses or mitigations in place already.