Security notice

Tailscale or headscale on your servers? Tailscale released a fix, headscale has not. Update and tighten your SSH settings today.

Last updated: Wednesday, October 28, 2026, 9:05 AM ETStatus: Fix released for Tailscale. headscale still unfixed.

On October 25, 2026, security researcher Erica Windisch of Cyberdione Labs published "Tailworm," a report on 11 flaws she found in Tailscale 1.104.2 and in headscale 0.29.5, the self-hosted server some teams run instead of Tailscale's own service. The most serious are in Tailscale SSH, a feature that lets one device log in to another. She says a single hacked device that is already allowed to connect can use SSH port forwarding to take full control of the server it connects to. This page originally said there was no fix and no security bulletin. That is superseded. On October 28 Tailscale released version 1.104.4 with fixes for the issues in its four security bulletins, TS-2026-014 to TS-2026-017, and no attacks have been reported. The self-hosted server headscale has no fix yet. See the October 28 update below. If your business or your developers use Tailscale or headscale, ask them today to update Tailscale and to tighten the settings listed below.

Update, October 28, 2026

Tailscale has released version 1.104.4, which it says fixes the Tailscale SSH and serve flaws. Update every machine that runs Tailscale. The self-hosted server headscale has no fix yet. No attacks have been reported. Our earlier text said there was no fix, no security bulletin and no patch. That is no longer true, and we have marked those lines below.

The fix is out. In a blog post dated October 28, Tailscale says the fixes "are now available in Tailscale v1.104.4" and recommends that anyone who uses Tailscale SSH update to that release or later. It published four security bulletins, TS-2026-014 to TS-2026-017, and says each lists the affected feature, the conditions needed, the impact and the fix. (Tailscale blog, Tailscale security bulletins)
What the four bulletins cover. TS-2026-014: SSH forwarding to Unix sockets could reach sockets only the administrator account should reach, such as the Docker socket or Tailscale's own control socket. TS-2026-015: an SSH session could use up the server's memory and crash the Tailscale program. TS-2026-016: forwarding with tailscale serve to a Unix socket could reach Tailscale's own control socket, which one of the issues allowed to take over the node. TS-2026-017: in one serve setup, a request could receive another mount's permission headers. As of our check, the bulletins use Tailscale's own TS numbers and we found no CVE numbers or severity scores on them. (Tailscale security bulletins, The Hacker News)
What Tailscale says it means. Tailscale says the SSH flaws were about what a session could do after it was allowed in, that using them needs an existing foothold on a device your policy already lets connect, and that an unauthenticated attacker cannot connect to arbitrary Tailscale SSH servers. It rejects the word "worm" and calls this "lateral movement limited to connections allowed by a tailnet policy file." Tailscale says three of the five serve and funnel findings were bugs that 1.104.4 fixes and two work as designed, and that the app connector finding is in an unreleased feature. The researcher called the chain "wormable" in her lab tests, and Tailscale rejects that description. (Tailscale blog, The Hacker News)
What the fix changes. The Hacker News reports that in 1.104.4 Tailscale changed its SSH server to carry out forwarding as the logged-in user rather than as the administrator account. Tailscale SSH's server runs only on Linux and the open-source macOS build. (The Hacker News)
If you cannot update yet. The workaround we listed below still stands: set TS_SSH_DISABLE_FORWARDING=1 in the environment of the Tailscale service and restart it. Tailscale's bulletin and The Hacker News say this turns off forwarding without turning off Tailscale SSH, and blocks several of the more serious findings. (Tailscale security bulletins, The Hacker News)
SSH "check mode" does not stop these flaws. Tailscale recommends reviewing SSH access rules and considering check mode, which asks a person to sign in again before a session starts, for sensitive systems. The Hacker News points out that check mode does not stop these forwarding flaws, because it guards the start of a session and the forwarding happens inside a session that has already been approved. Use it for what it does, not as a workaround for these flaws. (Tailscale blog, The Hacker News)
Updating does not cancel a stolen key. The Hacker News reports, citing the researcher's report, that a stolen device key stays valid until the device is deleted in the Tailscale admin console, because rebuilding the machine does not cancel it, and that Tailscale's notices do not cover this case. If you think a device was taken over, delete it as well as updating. (The Hacker News, Tailworm)
headscale has no fix yet. The report tested headscale 0.29.5. The newest headscale release we found, 0.29.6 of October 24, lists security work on certificate checks and software libraries but nothing for these findings. The Hacker News also says headscale 0.29.5 does not fix them, and Tailworm, in its status table updated October 28, lists its headscale finding as pending. The researcher says headscale cannot switch SSH forwarding off in its rules. We read this as follows: the SSH server runs in the Tailscale software on each machine, not in headscale, so updating those machines to 1.104.4 should close the SSH forwarding flaws there too. That is our reading, not a statement from Tailscale or headscale, so ask your developer to confirm. Until you have confirmed that every machine is updated, treat every SSH rule on a headscale network as allowing full control of the target. (headscale release notes, The Hacker News, Tailworm)
Still no attacks reported. The Hacker News says neither Tailscale nor the report says the flaws have been used in real attacks, and that the researcher's test code is not public. We found no report of attacks. (The Hacker News)

What to do

Update Tailscale to 1.104.4 or later on every machine, starting with servers that have Tailscale SSH or serve turned on. Turn on automatic updates if you can. If you run headscale, update the Tailscale software on its machines too, keep the settings steps below, and watch its releases for a fix. EverThread does not test for these flaws. Our scans check your site from the outside and cannot see whether your servers use Tailscale or headscale or which version they run. (Tailscale blog, Tailscale security bulletins, The Hacker News)

What happened

An unfixed report. The Tailworm report says it tested Tailscale 1.104.2 and headscale 0.29.5 in a lab from October 22 to 24, 2026. The researcher published it without waiting for a fix. She told The Hacker News she sent Tailscale the report and her test code before posting. (Tailworm, The Hacker News)
The main problem: Tailscale SSH port forwarding. Tailscale SSH checks which device is connecting and lets one access rule decide whether it may open a session. The report says that in a lab, an ordinary session using SSH port forwarding made Tailscale's own background program, which runs with full control of the machine, reach files that only the administrator account should touch. That gave the tester full control of the server. (Tailworm, The Hacker News)
What an attacker needs first. An attacker must already control one device that your Tailscale rules allow to connect to the target, and Tailscale SSH must allow port forwarding. This is a way to spread after a first break-in, not a way in from the internet. (Tailworm, The Hacker News)
"Wormable," in a lab. The researcher says one hacked device could spread to every device your rules allow it to reach. That spread was measured in a lab, not seen on real networks, and some other researchers have questioned the word "wormable." (The Hacker News)
Eleven findings in all. The others cover Tailscale's experimental app connectors, its serve and funnel features, the relay client and headscale, where an unauthenticated visitor could crash the server. The severity labels are the researcher's own, not official scores. Nobody else has publicly repeated her tests. (Tailworm, The Hacker News)
Tailscale's response on October 27. The fix has since been released; see the October 28 update above. Tailscale's vice president of engineering said the company had received the report and was already looking at the same area. On October 27 the company said most of the issues it found are privilege escalation: a user already allowed to connect "may be able to perform actions beyond the permissions of their configured local user." It called them "serious security issues," said fixes were built and being tested, and said it is "targeting a release within the next 24 hours." It said it will publish an advisory once the patch ships. It has not confirmed every claim in the report. (The Hacker News, Tailworm upstream response)
Superseded on October 28: the bulletins and the fix are out. Still no attacks reported. When we checked on October 27, 2026, Tailscale's security bulletins page listed nothing for these findings, and 1.104.2 was still the newest Tailscale release. We found no report of attacks on real networks. (Tailscale security bulletins, The Hacker News)

Who should worry

This is a tool for technical teams. It matters if someone you rely on uses it to reach servers.

Your developer, agency or IT provider reaches your servers over Tailscale, especially with Tailscale SSH turned on.
You run headscale, the self-hosted version. The report says forwarding cannot be switched off per rule on headscale 0.29.5, so every SSH rule there should be treated as allowing full control of the target. There is no headscale fix as of October 28; see the update above for what updating the Tailscale software does. (The Hacker News)
You use Tailscale app connectors, serve or funnel on servers that hold customer data.

What to do now

Do these today. The Tailscale update is out now, so installing it (step 7) comes first.

Ask the question. Send the message below to whoever runs your Tailscale or headscale. You need to know whether Tailscale SSH is on and which devices are allowed to use it.
Turn off SSH port forwarding where it is not needed. Tailscale says this can be done per rule on its hosted service, or for the whole machine by setting TS_SSH_DISABLE_FORWARDING=1 for the Tailscale service and restarting it. Tailscale says this keeps Tailscale SSH working and reduces several of the more serious findings. (The Hacker News)
Tighten who may connect. Write SSH rules for one named device to one named target, and remove broad rules that cover a whole group or tag. The report says this was the one control that stopped the spread in its tests. (Tailworm, The Hacker News)
Consider turning on Tailnet Lock. This Tailscale feature requires new devices to be signed before they can join. In the report's lab, the chain that added a rogue device to the network did not finish on networks with Tailnet Lock on. (The Hacker News)
Consider turning off Tailscale SSH on important servers. The researcher advises this. Tailscale says it is "not recommending that everyone disable Tailscale SSH," because whether a setup is at risk depends on its permissions and settings. Your developer should decide for each server. (The Hacker News)
Remove extra permissions. Take app connector permissions away from devices that do not need them, and turn on key expiry. (The Hacker News)
Install the Tailscale update now: version 1.104.4 or later. Turn on automatic updates if you can. Tailscale's bulletins TS-2026-014 to TS-2026-017 say 1.104.4 contains the fixes. This step earlier said Tailscale had not published a fixed version number; that is superseded. There is no headscale fix yet, so watch its releases. (The Hacker News)
If a device may be hacked, delete it in the Tailscale admin console. Rebuilding the machine does not cancel keys an attacker may already have copied. (The Hacker News)

What to send your developer, agency or host

A researcher published the Tailworm report on October 25, 2026, describing 11 flaws, unfixed when it was published, in Tailscale 1.104.2 and headscale 0.29.5, mainly privilege escalation through Tailscale SSH Unix socket forwarding. Tailscale announced on October 28 that version 1.104.4 fixes the issues in its bulletins TS-2026-014 to TS-2026-017. No attacks have been reported. There is no headscale fix yet. Please tell me today: do we use Tailscale or headscale? Is Tailscale SSH turned on, and is port forwarding allowed? Can we disable forwarding (TS_SSH_DISABLE_FORWARDING=1), narrow our SSH rules to single device pairs, remove unneeded app connector permissions, and turn on Tailnet Lock and automatic updates? Please tell me which Tailscale version each machine runs and install 1.104.4 or later. Please also tell me whether we run headscale and, if so, what you plan to do until it has a fix. Sources: the Tailworm report and The Hacker News.

Common questions

Has my business been hacked?

This notice does not mean your business has been hacked. The report describes tests in a lab, and we found no report of attacks on real networks. It means Tailscale has released a fix, so install it, and headscale has not, so tighten settings there until it does. (The Hacker News)

Can EverThread tell me if I am affected?

No. EverThread checks your website from the outside, the way a browser sees it. We do not test for these Tailscale or headscale flaws, and our scan cannot see whether your servers use Tailscale, which version they run or how it is set up. Your developer or host can check that. Our free scan looks at your home page from the outside for other common problems, such as an expired padlock certificate, missing browser safety settings and files that should not be public.

Is Tailscale fixed? What about headscale?

Tailscale is fixed in version 1.104.4, so update. The earlier answer here said there was nothing to install yet; that is superseded. The headscale server is separate software run by its own project, and as of October 28 its newest release lists no fix for these findings. We have not seen a report of attacks. The researcher and Tailscale still disagree about some details, such as whether "wormable" is the right word. (Tailscale blog, headscale release notes, Tailworm)

Where can I follow official updates?

Tailscale lists confirmed issues on its Tailscale security bulletins page and its changelog. The researcher's report is at tailworm.com.

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Sources

Erica Windisch, Cyberdione Labs: Tailworm, security assessment of Tailscale v1.104.2 and headscale v0.29.5, October 25, 2026, upstream response section updated October 27, 2026
The Hacker News: Unpatched Tailscale SSH Flaws Could Let a Hacked Device Reach Root on Other Servers, October 25, 2026, updated October 27, 2026
Tailscale: Security bulletins, checked October 27, 2026
Tailscale: Tailscale SSH: Findings and fixes, Mike Shaver, October 28, 2026
Tailscale: Security bulletins TS-2026-014 to TS-2026-017, checked October 28, 2026
The Hacker News: Tailscale Patches SSH Flaws That Could Let Hacked Devices Gain Root Access on Other Servers, Swati Khandelwal, October 28, 2026
headscale: v0.29.6 release notes, October 24, 2026, checked October 28, 2026
Tailworm: status of each finding after the Tailscale release, checked October 28, 2026