Budibase: Email Change IDOR via POST /api/v2/email allows full Account Takeover (accountId not validated against session)

Summary

POST /api/v2/email on the account portal (account.budibase.app) starts an email-change workflow using a client-supplied accountId that is not validated against the authenticated session. A logged-in attacker supplies a victim's accountId and an email address they control; the verification code is delivered to the attacker's address, and completing the workflow changes the victim's account email. The attacker then password-resets the victim's account through the controlled address and logs in — full account takeover with no victim interaction.

Vulnerability Details

The endpoint session-checks the currentEmail field (a mismatch returns 403), but it does not enforce body.accountId === session.accountId. The account-portal frontend only ever submits the logged-in user's own accountId, so in normal use the two always match — the server simply trusts the body value. An attacker who has a victim's accountId can point the workflow at the victim's account while passing their own currentEmail to clear the session check.

This is more powerful than a direct password reset: PUT /api/v2/auth/password {email} already exists and is gated only on knowing the victim's email, but the reset link is sent to the address on the account — the victim's inbox, which the attacker does not control. This IDOR moves the victim's email to an attacker-controlled inbox first, so the attacker receives the reset link and sets a password they know.

accountId obtainability. We checked every endpoint reachable from a non-admin free-tier account — GET /api/global/users (no UUID in any user record), GET /api/global/auditlogs/search (no accountId field), GET /api/global/users/invites (code + email + name only), GET /api/v2/tenant (one tenant-internal UUID, not a user accountId), the account-portal frontend (passes the session's own accountId only), and all unauthenticated endpoints — and the victim's accountId was not present in any of them. The attacker must obtain the UUID through some channel other than the normal API surface (support channel, screenshot, a leak, prior compromise, etc.).

Steps to Reproduce

Setup: Two account-portal accounts at https://account.budibase.app — Account A (attacker) and Account B (victim). From Account B's session, GET /api/auth/self returns account.accountId — this is the value the attacker needs.

1. Start the email-change workflow pointed at the victim's accountId, newEmail = attacker-controlled.

POST /api/v2/email HTTP/1.1
Host: account.budibase.app
Content-Type: application/json
Cookie: budibase:auth=<ACCOUNT_A_JWT>

{"currentEmail":"<ACCOUNT_A_EMAIL>","newEmail":"attacker-controlled@example.net","accountId":"<VICTIM_ACCOUNT_ID>"}

Response: 201 Created, sets budibase:change_email:correlationkey (HttpOnly), :instancekey, :status, :newemail cookies. The workflow started against the victim's accountId even though the caller is Account A.

2. Complete the change with the code from the attacker-controlled inbox (or read directly from the correlationkey cookie set in step 1).

POST /api/v2/email/verification HTTP/1.1
Host: account.budibase.app
Content-Type: application/json
Cookie: budibase:auth=<ACCOUNT_A_JWT>; budibase:change_email:correlationkey=<CODE>; budibase:change_email:instancekey=<KEY>

{"verificationCode":"<code>","processInstanceKey":"<key>"}

Response: 200 OK. The victim's account email is now attacker-controlled@example.net.

3. Confirm the change hit the victim, not the caller (false-positive control).

• Account A (caller) still logs in with its own original email — 200, unchanged.
• Account B's (victim) original email is now rejected — 403, locked out.
• attacker-controlled@example.net now logs into the victim's account — 200.

4. Take over the account.

PUT /api/v2/auth/password HTTP/1.1
Host: account.budibase.app
Content-Type: application/json

{"email":"attacker-controlled@example.net"}

Response: 202 Accepted, reset link delivered to the attacker's own inbox. Complete the reset with PUT /api/v2/auth/password/verification, then log in as the victim with the attacker-chosen password. GET /api/auth/self afterward returns the victim's real accountId and tenantId — full account takeover, confirmed via a genuinely separate account/tenant (not a same-account self-test).

Impact

An authenticated account-portal user who obtains a victim's accountId (out-of-band — it is not exposed anywhere in the normal cross-user API surface we could find) can take over that victim's account: rewrite the login email to an attacker address, set a new password, and access the victim's tenants, apps, and stored datasource credentials (REST/SQL/S3 auth). The victim is locked out of their own account. Every step from the initial IDOR write to full login-as-victim is deterministic and 100% reliable once the accountId is known — no additional vulnerability or guessing is required, since the chain uses nothing but the platform's own stock password-reset flow.

Remediation

Validate that the body's accountId equals the authenticated session's accountId before starting or completing the email-change workflow (the same check already applied to currentEmail). Do not trust a client-supplied accountId to select the workflow target.