Hello, The CMSG_DATA() fix requires bumping the ABI. Since it's still really at early stage, I don't plan to make a compatibility layer or such, and just rebuild all the packages using CMSG_DATA (~500 packages). One such package is openssh, which means that if you upgrade your libc0.3, the old openssh will break. I have put a Breaks so people don't accidentally end up there. But installing the rebuilt openssh will not currently upgrade libc0.3, so be sure to upgrade both packages on your hurd-amd64 system.
So basically, after next "unreleased" mirror pulse (~7:30 UTC), make sure to install libc0.3 (>= 2.40-6~1) and openssh-server (>= 9.9p1-3+hurd.1) at the same time and you'll be good, you won't lose your ssh server access. hurd-i386 is not affected at all by all of this. Samuel