A New Kali Linux Archive Signing Key | Kali Linux Blog
TL;DR Bad news for Kali Linux users! In the coming day(s), apt update is going to fail for pretty much everyone out there: Missing key 827C8569F2518CC677FECA1AED65462EC8D5E4C5, which is needed to verify signature. Reason is, we had to roll a new signing key for the Kali repository. You need to download and install the new key manually, here’s the one-liner:
Kali Linux