An issue was discovered in OpenSSH 7.9. Due to the scp implementation being derived from 1983 rcp, the server chooses which files/directories are sent to the client. However, the scp client only performs cursory validation of the object name returned (only directory traversal attacks are prevented). A malicious scp server (or Man-in-The-Middle attacker) can overwrite arbitrary files in the scp client target directory. If recursive operation (-r) is performed, the server can manipulate subdirectories as well (for example, to overwrite the .ssh/authorized_keys file).

Affected: Ubuntu:14.04:LTS: openssh, Ubuntu:16.04:LTS: openssh, Ubuntu:18.04:LTS: openssh

Harry Sintonen discovered multiple issues in the OpenSSH scp utility. If a user or automated system were tricked into connecting to an untrusted server, a remote attacker could possibly use these issues to write to arbitrary files, change directory permissions, and spoof client output.