VyOS 1.3 through 1.5 (fixed in 1.4.2) or any Debian-based system using dropbear in combination with live-build has the same Dropbear private host keys across different installations. Thus, an attacker can conduct active man-in-the-middle attacks against SSH connections if Dropbear is enabled as the SSH daemon. I n VyOS, this is not the default configuration for the system SSH daemon, but is for the console service. To mitigate this, one can run "rm -f /etc/dropbear/key" and/or "rm -f /etc/dropbear-initramfs/key" and then dropbearkey -t rsa -s 4096 -f /etc/dropbearrsahostkey and reload the service or reboot the system before using Dropbear as the SSH daemon (this clears out all keys mistakenly built into the release image) or update to the latest version of VyOS 1.4 or 1.5. Note that this vulnerability is not unique to VyOS and may appear in any Debian-based Linux distribution that uses Dropbear in combination with live-build, which has a safeguard against this behavior in OpenSSH but no equivalent one for Dropbear.

A privilege escalation issue was discovered in VyOS 1.1.8. The default configuration also allows operator users to execute the pppd binary with elevated (sudo) permissions. Certain input parameters are not properly validated. A malicious operator user can run the binary with elevated permissions and leverage its improper input validation condition to spawn an attacker-controlled shell with root privileges.

A sandbox escape issue was discovered in VyOS 1.1.8. It provides a restricted management shell for operator users to administer the device. By issuing various shell special characters with certain commands, an authenticated operator user can break out of the management shell and gain access to the underlying Linux shell. The user can then run arbitrary operating system commands with the privileges afforded by their account.