{
  "guidislink": false,
  "id": "https://tailscale.com/security-bulletins/#ts-2026-006",
  "link": "https://tailscale.com/security-bulletins/#ts-2026-006",
  "links": [
    {
      "href": "https://tailscale.com/security-bulletins/#ts-2026-006",
      "rel": "alternate",
      "type": "text/html"
    }
  ],
  "published": "Thu, 11 Jun 2026 00:00:00 GMT",
  "summary": "\u003cp\u003e\u003cstrong\u003e\u003cem\u003eDescription\u003c/em\u003e\u003c/strong\u003e: Tailscale SSH allowed users to be addressed by numeric UID, bypassing \u003ccode\u003eroot\u003c/code\u003e user restrictions in ACLs.\u003c/p\u003e\n\u003ch4\u003eWhat happened?\u003c/h4\u003e\n\u003cp\u003e\u003ca href=\"https://tailscale.com/docs/features/tailscale-ssh\"\u003eTailscale SSH\u003c/a\u003e previously allowed users to be addressed by their username \u003cem\u003eor\u003c/em\u003e UID value, however the \u003ccode\u003eroot\u003c/code\u003e user restrictions in ACL enforcement only considered the former. A user with non-\u003ccode\u003eroot\u003c/code\u003e SSH access who addressed \u003ccode\u003e0@host\u003c/code\u003e would have been able to access \u003ccode\u003eroot\u003c/code\u003e in violation of ACLs.\u003c/p\u003e\n\u003cp\u003eTailscale now disallows the use of UIDs or numeric-only usernames via SSH to avoid this ambiguity.\u003c/p\u003e\n\u003cp\u003eThis vulnerability is fixed in Tailscale version 1.98.9 or newer.\u003c/p\u003e\n\u003ch4\u003eWhat was the impact?\u003c/h4\u003e\n\u003cp\u003eA user with SSH access to a node would have been able to SSH as \u003ccode\u003eroot\u003c/code\u003e using the username \u003ccode\u003e0\u003c/code\u003e in violation of ACL policy.\u003c/p\u003e\n\u003ch4\u003eWho was affected?\u003c/h4\u003e\n\u003cp\u003eUsers of Tailscale SSH on Linux/Unix hosts that rely on \u003ccode\u003eautogroup:nonroot\u003c/code\u003e user restrictions in Tailscale ACLs.\u003c/p\u003e\n\u003ch4\u003eWhat do I need to do?\u003c/h4\u003e\n\u003cp\u003eIf you use Tailscale SSH, upgrade to Tailscale version 1.98.9 or newer.\u003c/p\u003e\n\u003ch4\u003eCredits\u003c/h4\u003e\n\u003cp\u003eWe would like to thank Tim Hoffman (GM) for reporting this issue.\u003c/p\u003e",
  "summary_detail": {
    "base": "https://tailscale.com/security-bulletins/index.xml",
    "language": null,
    "type": "text/html",
    "value": "\u003cp\u003e\u003cstrong\u003e\u003cem\u003eDescription\u003c/em\u003e\u003c/strong\u003e: Tailscale SSH allowed users to be addressed by numeric UID, bypassing \u003ccode\u003eroot\u003c/code\u003e user restrictions in ACLs.\u003c/p\u003e\n\u003ch4\u003eWhat happened?\u003c/h4\u003e\n\u003cp\u003e\u003ca href=\"https://tailscale.com/docs/features/tailscale-ssh\"\u003eTailscale SSH\u003c/a\u003e previously allowed users to be addressed by their username \u003cem\u003eor\u003c/em\u003e UID value, however the \u003ccode\u003eroot\u003c/code\u003e user restrictions in ACL enforcement only considered the former. A user with non-\u003ccode\u003eroot\u003c/code\u003e SSH access who addressed \u003ccode\u003e0@host\u003c/code\u003e would have been able to access \u003ccode\u003eroot\u003c/code\u003e in violation of ACLs.\u003c/p\u003e\n\u003cp\u003eTailscale now disallows the use of UIDs or numeric-only usernames via SSH to avoid this ambiguity.\u003c/p\u003e\n\u003cp\u003eThis vulnerability is fixed in Tailscale version 1.98.9 or newer.\u003c/p\u003e\n\u003ch4\u003eWhat was the impact?\u003c/h4\u003e\n\u003cp\u003eA user with SSH access to a node would have been able to SSH as \u003ccode\u003eroot\u003c/code\u003e using the username \u003ccode\u003e0\u003c/code\u003e in violation of ACL policy.\u003c/p\u003e\n\u003ch4\u003eWho was affected?\u003c/h4\u003e\n\u003cp\u003eUsers of Tailscale SSH on Linux/Unix hosts that rely on \u003ccode\u003eautogroup:nonroot\u003c/code\u003e user restrictions in Tailscale ACLs.\u003c/p\u003e\n\u003ch4\u003eWhat do I need to do?\u003c/h4\u003e\n\u003cp\u003eIf you use Tailscale SSH, upgrade to Tailscale version 1.98.9 or newer.\u003c/p\u003e\n\u003ch4\u003eCredits\u003c/h4\u003e\n\u003cp\u003eWe would like to thank Tim Hoffman (GM) for reporting this issue.\u003c/p\u003e"
  },
  "title": "TS-2026-006",
  "title_detail": {
    "base": "https://tailscale.com/security-bulletins/index.xml",
    "language": null,
    "type": "text/plain",
    "value": "TS-2026-006"
  }
}