Image: Tailworm

A security researcher has published a long report claiming 11 flaws in Tailscale, the popular tool for building private networks between devices. The report, called Tailworm, also covers headscale, an open source server that some people run in place of Tailscale's own. At the time of this writing, Tailscale has not confirmed the findings or released a fix.

The report is signed by Erica Windisch of Cyberdione Labs. It says the issues were found in Tailscale v1.104.2 and headscale v0.29.5 during testing from October 22 to 24, and that every finding was reproduced in a lab on unmodified software.

The biggest claim involves Tailscale SSH, a feature that lets approved devices log in to each other over the network. According to the report, the feature handles some file forwarding as the root user, the most powerful account on a machine. Windisch says that lets someone with ordinary SSH access trick it into giving them root on the other server. From there, the report says, an attacker could steal the keys used to add new devices and sneak their own machine into the network.

The report also says app connectors, an experimental feature, can be used to reach places a company's network rules are supposed to block, such as cloud credential services. Other findings cover crashing a self hosted headscale server without logging in and a way around access checks in the tailscale serve feature.

The name comes from the report's worm test. In its lab, the report says, an attacker could spread automatically to every device the SSH rules allowed, in under a second per hop. That only works if an attacker already controls one device, through something like a hacked web app or a poisoned software package.

How Windisch went public has drawn as much attention as the bugs. She did not give Tailscale time to ship fixes first. Writing on Hacker News, she said the problems were reported but not coordinated, and that in her view infrastructure is vulnerable today. The report itself says the researchers are not linked to Tailscale and were not paid for the work.

‼️ Researcher Erica Windisch skipped coordinated vulnerability disclosure and published 11 unpatched Tailscale flaws.

In her lab, Tailscale SSH race conditions let one hacked device get root on other servers and add a rogue node.

— International Cyber Digest (@IntCyberDigest) October 25, 2026

Not everyone is convinced by the framing. Some developers on X said the SSH bug is serious but only affects people who turned on Tailscale's own SSH server, and that any spread is limited by the SSH rules an admin sets.

that tailworm site reads like gigaslop, i call bullshit on the framing.

the ssh bug is basically: authorized nonroot access can become root via unix socket forwarding. serious, but propagation follows ssh policy. this concerns tailscale’s opt-in ssh server, not ordinary openssh.

— banteg (@banteg) October 25, 2026

Tailscale's security bulletins page listed no entry for the Tailworm findings at the time of this writing, and no CVE numbers had been assigned. Cyber Security News also reported that Tailscale had not confirmed the issues. None of the findings have been independently verified so far.

What Tailscale users can do now

The report suggests a few steps while there is no patch. If you use Tailscale SSH, limit rules to specific pairs of machines instead of whole groups, and never allow logins to root. On the hosted Tailscale service, the report says SSH forwarding can be switched off per rule. On headscale it cannot, so the report advises treating any SSH access there as root access. Remove the app connector permission from devices that do not need it, and keep self hosted headscale servers behind memory limits.

If you do not use Tailscale SSH, app connectors or headscale, the report's most serious findings do not appear to apply to you.