Server: Budibase: Privilege escalation via public role assignment API missing app-level authorization (CVE-2026-73305)
Affects @budibase/serverSource GCVE Database
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HWhat to do
AI-suggested
Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is available, restrict app-scoped builder roles carefully and monitor for suspicious role-assignment API usage. Avoid exposing the public role-assignment API to untrusted users. Review and harden authorization logic to ensure app-level role assignments require verification that the caller controls the target app. Follow vendor updates for a security patch addressing this missing authorization check.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| npm@budibase/server | Affected
| Fixed in– |
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Description
### Summary Budibase `3.39.19` (commit `03fbabae4`) is affected by a privilege-escalation / missing-authorization flaw in the public role-assignment API. An **app-scoped builder** (a user who builds only specific apps — `user.builder.apps = [appA]`, not a global builder or admin) can grant **themselves builder access to ANY other app in the tenant**, or assign themselves/any user an arbitrary data-plane role (e.g. `ADMIN`) in any app, by calling `POST /api/public/v1/roles/assign`. The endpoint only authorizes the two *global* flags (`admin`, `builder`); the per-app `appBuilder` and `role:{appId,roleId}` grant vectors are passed to the backend **without any authorization check that the caller controls the target app**. Reproduced in a local authorized lab using the verbatim authorization-gate and SDK logic. This is an incomplete fix of the role-assignment hardening in commit `d63d1d9054` ("Inline public user global role validation"), which only ever validated the global flags. ### Details The issue is caused by authorization being implemented as a **flag-level allowlist** (`admin`/`builder`) instead of validating the *scope* the caller is granting. Relevant code paths: - `packages/server/src/api/controllers/public/globalRoleValidation.ts` — `validateGlobalRoleUpdate(ctx, roleUpdate)` only checks `roleUpdate.admin` (requires `isAdmin`) and `roleUpdate.builder` (requires `isGlobalBuilder`). The `GlobalRoleUpdate` interface declares only `{ builder?, admin? }`; `appBuilder` and `role` are not referenced. - `packages/server/src/api/controllers/public/roles.ts` — `assign()` does `const { userIds, ...assignmentProps } = ctx.request.body; validateGlobalRoleUpdate(ctx, assignmentProps); await sdk.publicApi.roles.assign(userIds, assignmentProps)`. The `appBuilder`/`role` props pass through unvalidated. - `packages/pro/src/sdk/publicApi/roles.ts` — `assign()`: for `opts.appBuilder` it sets `user.builder = { apps: existing.concat([getProdWorkspaceID(opts.appBuilder.appId)]) }`; for `opts.role` it sets `user.roles[getProdWorkspaceID(opts.role.appId)] = opts.role.roleId`. No check that the caller builds the target app, and `userIds` is an arbitrary list (`bulkGet`). The only gate is the `isExpandedPublicApiEnabled()` license check. - `packages/server/src/api/routes/public/index.ts` — `applyAdminRoutes(roleEndpoints)` attaches **only** `middleware.builderOrAdmin` (no `publicApi`, no `authorized(PermissionType.USER, …)`). - `packages/backend-core/src/middleware/builderOrAdmin.ts` — with a `workspaceId` present, it only requires `isBuilder(ctx.user, workspaceId)`. The attacker sets `x-budibase-app-id` to **their own** app (appA), so the gate passes. - `packages/backend-core/src/middleware/builderOnly.ts` — on the worker, `POST /api/global/self/api_key` only requires `hasBuilderPermissions(ctx.user)`, which is true for app-scoped builders, so the attacker can self-issue a public API key. - `packages/shared-core/src/sdk/documents/users.ts` — `isGlobalBuilder` is false for app-scoped builders (so the global `builder` flag is correctly blocked), while `isBuilder(user, appA)` and `hasBuilderPermissions(user)` are true. Attack flow: 1. Attacker is an app-scoped builder of `appA` only (no global builder/admin). 2. `POST /api/global/self/api_key` (worker) — passes `builderOnly` via `hasBuilderPermissions` → attacker obtains a public API key. 3. `POST /api/public/v1/roles/assign` with header `x-budibase-app-id: <appA prod id>` and body `{"userIds":["<self>"],"appBuilder":{"appId":"<appB>"}}` — `builderOrAdmin` passes (`isBuilder(user, appA)`), `validateGlobalRoleUpdate` ignores `appBuilder`, the SDK pushes `appB` into `user.builder.apps`. 4. Attacker is now a builder of `appB` (and, via the `role` vector, can set any data-role such as `ADMIN` in any app). Security boundary crossed: - **Before:** builder of `appA` only. - **After:** builder of `appB` (and any other app) → read/modify all rows, read datasource configs and exfiltrate stored datasource credentials, edit automations (including the `bash`/`executeScript`/`executeQuery` steps); plus arbitrary data-role assignment in any app. - **Why disallowed:** the per-app builder model is meant to isolate builders to their assigned apps; a builder of one app must not gain authority over apps they were never granted. ### PoC Environment: - Budibase version: `3.39.19`, commit `03fbabae4` - Deployment: Business/Enterprise license required (`isExpandedPublicApiEnabled`) - Attacker role: app-scoped builder (`user.builder.apps=[appA]`), not global builder/admin - Mock services: none needed for the unit-level proof; HTTP PoC script provided for a licensed lab Steps (unit-level proof, no license needed — verbatim auth-gate + SDK logic): 1. Run the verification harness: ```bash cd D:/CVE-Hunting/budibase-audit-output/lab node harness/verify-privesc-authz.cjs ``` 2. Observed result (evidence: `evidence/lab-privesc-authz.log`): ```text [PASS-VALIDATION] appBuilder:{appId:APP_B}