I looked into this a bit yesterday. As mentioned in the issue upstream at https://github.com/etcd-io/etcd/issues/9353, the fix has been merged in the master branch of etcd in March 2018, almost a year ago. The conversation also mentions that this will be part of the next release v3.4. However v3.4 has not been released yet.
And I don't think we want to package a random commit from the master branch of etcd. So if we want to solve this bug simply by updating the package, we'll have to wait for v3.4 to be released. The other alternative is to cherry-pick the patch. If I'm not mistaken, the fix can be found in this MR: https://github.com/etcd-io/etcd/pull/9372/files. It's not a trivial patch. It's unlikely that we can apply it without modification on the etcd currently packaged in debian. I personally can't do that, as I know nothing about etcd anyway. I don't know if someone feels up to the task, or have a better idea about how to solve that. Cheers, Arnaud