Yes, it specifically affects the Alpine/musl interaction. It’s a vulnerability in how Alpine interfaces with musl, and allows anyone who can reach your SSH port to instantly log into a passwordless account by entering over 256 characters into the password field.

The vuln is nicknamed *sshole, if you want to search it. Because it only works on passwordless accounts, (meaning it has a * in the password field). And the most common use-case for passwordless accounts is because you’re using cert-based authentication instead. Thus the warnings that if you’re using cert-only SSH, you’re most likely vulnerable.