CVSS 6.8 CVE-2019-6110
CVSS 6.8 CVSS:3.0/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N
In OpenSSH 7.9, due to accepting and displaying arbitrary stderr output from the server, a malicious server (or Man-in-The-Middle attacker) can manipulate the client output, for example to use ANSI control codes to hide additional files being transferred.
Test with SSH-MITM
A proof of concept exploit is integrated in ssh-mitm.
This exploit also integrates CVE-2019-6111 to inject additional files.
To inject files during a file transfer from the server to the client you have to start ssh-mitm with following arguments:
$ ssh-mitm server --scp-interface inject_file --scp-inject /path/to/additional/file
The file transfer for the injected file will be hidden because of the described vulnerability and CVE-2019-6109.