Comment 26 for bug 1816846

When glibc was *uploaded* isn't meaningful here, it's when it was released to -updates, which was the 20th, and is when people started seeing this issue. Unfortunately, the NSS ABI is easily perturbed and seemingly unrelated changes can break it.

The "right" fix would be to attempt re-exec any long-running process under d-i after updating libc6-udeb (or just refuse to update libc6 at all in the installer environment), but that's not likely to happen in xenial.

The easier fix on events like this is, indeed, use the netboot images built with the newer glibc. Expecting old netboot images to work forever is a nice pipe dream, but has never actually been realistic in practice.

TL;DR: Update to the latest xenial-updates netboot images, and the problem will resolve itself.