Tailscale Exposed with 11 Security Issues: Installed a Security Door for Servers, but May Let Hackers Take the Master Key

Beating AI News Flash: Recently, many developers have suggested that one of the best ways to protect a VPS is to close the public SSH entry point and switch to Tailscale for remote access.

As a result, on October 25, security researcher Erica Windisch published a report titled Tailworm, identifying 11 security issues in Tailscale and its open-source alternative headscale. The most serious case occurs precisely in Tailscale's built-in SSH feature.

Attackers do not need to crack the VPN. As long as they control a device that has already been authorized to access the target server via Tailscale SSH, and SSH forwarding permissions are open, they may further seize root privileges on the server.

The vulnerability lies in privilege isolation: the Tailscale backend runs as root, and some SSH forwarding operations also inherit this privilege. In experiments, researchers used Unix Socket forwarding to bypass ordinary account restrictions and successfully obtained server root privileges through Docker.

Another attack chain also intercepted the device registration key and added a fake server to a test network where Tailnet Lock was not enabled.

Tailscale only fixed the SSH Unix Socket forwarding privilege escalation vulnerability in June this year. In the same month, it also closed a vulnerability that allowed obtaining root through digital user ID `0`; in July, it fixed an issue that bypassed permission restrictions through the special username `-i`. A few months later, researchers once again found a privilege escalation path in the same built-in SSH forwarding mechanism.

Tailscale Vice President of Engineering Mike Shaver subsequently acknowledged that the team had discovered the privilege boundary issue after SSH authorization, but had not yet confirmed all the conclusions of the research report, and did not recommend that all users directly disable Tailscale SSH.

On October 25, the engineering team continuously submitted multiple SSH redesign proposals on GitHub, preparing to make forwarding operations use the privileges of the actual logged-in user rather than directly handing them to the root process for execution. The relevant fixes have not yet been released in an official version.