CVE-2026-53514: Better auth Better Auth Vulnerable To Unauthorized Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-fmh4-wcc4-5jm3",
  "modified" : "2026-07-20T19:24:41Z",
  "published" : "2026-07-07T20:54:51Z",
  "aliases" : [ "CVE-2026-53514" ],
  "summary" : "Better Auth vulnerable to unauthorized invitation acceptance via unverified email match in organization plugin",
  "details" : "### Am I affected?\n\nUsers are affected if all of the following are true:\n\n- Their application uses `better-auth` with the `organization` plugin (`import { organization } from \"better-auth/plugins/organization\"`).\n- Their application enables a sign-up surface that allows arbitrary unverified email registration. Most commonly `emailAndPassword: { enabled: true }` without `requireEmailVerification: true`.\n- Their application has not set `requireEmailVerificationOnInvitation: true` on the `organization()` options.\n- Their application invitation distribution flow allows anyone other than the invited mailbox owner to obtain the `invitationId`. Examples: admin UI surfacing the link, copy-paste into chat, forwarded email, mail-forwarding rules at the recipient's domain, link previews logging the URL, or a custom `sendInvitationEmail` integration that sends to a non-owner channel.\n\nIf their application set `emailAndPassword: { enabled: true, requireEmailVerification: true }` so unverified rows cannot reach a usable session, they are not affected. Setting `requireEmailVerificationOnInvitation: true` closes `acceptInvitation` and `rejectInvitation`, but `getInvitation` and `listUserInvitations` remain ungated even with that flag.\n\nFix:\n\n1. Upgrade to `better-auth@1.6.11` or later.\n2. If developers cannot upgrade their application, see workarounds below.\n\n### Summary\n\nThe organization plugin's `acceptInvitation` endpoint trusts an email-string equality check as proof that the session user owns the invited address. With Better Auth's stock `emailAndPassword: { enabled: true }` configuration, `requireEmailVerification` defaults to `false`, so an attacker can sign up a row keyed to `victim@target.example` (auto-signed-in, `emailVerified: false`) before the legitimate owner. When an organization admin invites that address, the attacker presents the `invitationId` and accepts the invitation, joining the organization at the invited role.\n\n### Details\n\nThe recipient gate compares `invitation.email.toLowerCase()` to `session.user.email.toLowerCase()` and returns 403 on mismatch. The opt-in `requireEmailVerificationOnInvitation` flag adds an `emailVerified` check, but it defaults to `false` and only fires on `acceptInvitation` and `rejectInvitation`; `getInvitation` and `listUserInvitations` have no `emailVerified` gate at all.\n\nThe bearer token (`invitationId`) is by default 32 chars over `[a-zA-Z0-9]` (~190 bits), so the realistic attack vector is leakage of the invitation link rather than brute force.\n\nThe fix shape defaults the `emailVerified` gate to on and extends it across all four invitation endpoints (`acceptInvitation`, `rejectInvitation`, `getInvitation`, `listUserInvitations`). This is the same trust-primitive class as GHSA-g38m-r43w-p2q7 (OAuth auto-link); both ship the rule \"email equality is not ownership proof; both sides must prove ownership\".\n\n### Patches\n\nFixed in `better-auth@1.6.11`. All four invitation recipient endpoints (`acceptInvitation`, `rejectInvitation`, `getInvitation`, `listUserInvitations`) now require the session user's `emailVerified` to be `true` in addition to the email-string match. The `requireEmailVerificationOnInvitation` option default flips from `false` to `true`, so applications are secure out of the box.\n\n`getInvitation` and `listUserInvitations` use the new `EMAIL_VERIFICATION_REQUIRED_FOR_INVITATION` error code so the wording matches the operation; `acceptInvitation` and `rejectInvitation` keep the existing `EMAIL_VERIFICATION_REQUIRED_BEFORE_ACCEPTING_OR_REJECTING_INVITATION` code. Server-side calls to `listUserInvitations` that pass `ctx.query.email` without an authenticated session continue to bypass the gate; the gate is specific to session-authenticated recipient calls.\n\nIntegrators who intentionally accept invitations on unverified sessions can preserve the legacy permissive behavior with `organization({ requireEmailVerificationOnInvitation: false })`. The option is marked `@deprecated`; the gate at each call site carries a `FIXME` pointing at the next-minor follow-up that drops the option and makes the check unconditional. Operators that take this opt-out should understand the takeover risk before doing so.\n\n### Workarounds\n\nIf developers cannot upgrade their applications immediately:\n\n- **Set `organization({ requireEmailVerificationOnInvitation: true })`**. Closes `acceptInvitation` and `rejectInvitation` against unverified sessions. Does not close `getInvitation` or `listUserInvitations`.\n- **Set `emailAndPassword.requireEmailVerification: true`** (or remove email/password sign-up entirely). Closes the pre-registration step itself.\n- **Layer middleware** on the organization invitation routes that asserts `session.user.emailVerified === true` and rejects otherwise.\n\n### Impact\n\n- **Account takeover via pre-account hijacking on the org invitation surface**: the attacker, holding only an unverified self-issued session and the leaked `invitationId`, joins the organization as a member at the invited role.\n- **Organization membership reach**: the attacker reads invitation contents and any organization-scoped data the joined role can see, and acts as a member of the victim organization.\n\n### Credit\n\nReported by @widavies.\n\n### Resources\n\n- [CWE-287: Improper Authentication](https://cwe.mitre.org/data/definitions/287.html)\n- [CWE-345: Insufficient Verification of Data Authenticity](https://cwe.mitre.org/data/definitions/345.html)\n- [CWE-862: Missing Authorization](https://cwe.mitre.org/data/definitions/862.html)\n- [CWE-441: Unintended Proxy or Intermediary](https://cwe.mitre.org/data/definitions/441.html)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "better-auth"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.6.11"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/better-auth/better-auth/security/advisories/GHSA-fmh4-wcc4-5jm3"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-53514"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/better-auth/better-auth/pull/9577"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/better-auth/better-auth/commit/23094a628f007f801be6d26e5b15dc5fc6fc4eb8"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/better-auth/better-auth"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/better-auth/better-auth/releases/tag/v1.6.11"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-287", "CWE-345", "CWE-441", "CWE-862" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-07T20:54:51Z",
    "nvd_published_at" : "2026-07-15T18:16:47Z"
  }
}