Editor’s note, as of 2025-08-27: tmate.io and the tmate project have not been updated since fall 2019, so security vulnerabilities that may have arisen since then may not have been addressed. The tool is no longer recommended.
Especially in the current situation surrounding COVID-19, a functioning remote maintenance/remote control solution is extremely important.
It has been clear for some time, and not just since the discovery of massive security problems affecting several well-known providers, that there is a broad attack vector here.