Researcher Shows How One Compromised Device Could Lead to Root Access on Tailscale Networks

A security researcher has published findings showing that a single hacked device on a Tailscale network could be used to gain root access to other servers it is allowed to reach. The report, called Tailworm, was written by Erica Windisch of Cyberdione Labs and published on October 25. It was tested over three days in a lab on Tailscale 1.104.2 and headscale 0.29.5, a self-hosted server some networks use instead of Tailscale's hosted service. It describes lab tests, not attacks on real networks.

The attack needs two conditions: Tailscale SSH set up to allow port forwarding, and an attacker who already controls a device that the network's access rules permit to connect to the target. No stolen passwords or keys are required, because Tailscale SSH identifies the device rather than the user. The report says an attacker could gain that first foothold in the usual ways, such as a vulnerable web application, a poisoned software package, phishing or stolen logins. In the lab, an ordinary session using standard port forwarding led to root access.

What administrators can do depends on their setup. On Tailscale's hosted service, forwarding can be switched off per rule. On headscale 0.29.5 it cannot be turned off, so the report says every SSH grant should be treated as giving root on the target. As of publication, Tailscale had issued no security bulletin, CVE or fixed version. Its vice president of engineering, Mike Shaver, said on Reddit that the company has found issues it is working to fix and is not recommending that everyone disable Tailscale SSH.