Command Injection using malicious hostname in expanded proxycommand

Using the ProxyCommand or the ProxyJump feature enables users to exploit unchecked hostname syntax on the client, which enables to inject malicious code into the command of the above-mentioned features through the hostname parameter. User interaction is required to exploit this issue. Advisory from libssh: https://www.libssh.org/security/advisories/CVE-2023-6004.txt Advisory from OpenSSH which also suffered from this flaw: https://www.openssh.com/txt/release-9.6 ## Impact Code execution via malicious input hostname or other tokens