In NetKit through 0.17, rcp.c in the rcp client allows remote rsh servers to bypass intended access restrictions via the filename of . or an empty filename. The impact is modifying the permissions of the target directory on the client side. This is similar to CVE-2018-20685.
https://sintonen.fi/advisories/scp-client-multiple-vulnerabilities.txt
https://lists.debian.org/debian-lts-announce/2021/11/msg00016.html