Budibase before 3.40.0 Identity Confusion via Chat-Link Handoff CSRF

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Budibase before 3.40.0 contains a cross-site request forgery vulnerability in the chat-link handoff endpoint that allows attackers to bind an external chat identity to a victim's account. Attackers can craft a phishing page that auto-submits a POST request with a leaked confirmation token to bind their chat identity to a victim user's account, enabling impersonation within agent operations and inheritance of victim permissions.

Source published

13 Aug 2026 21:54:41 UTC

Source modified

8 Oct 2026 15:24:34 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

CVSS 3.1 · 7.7 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N

Budibase before 3.40.0 contains a cross-site request forgery vulnerability in the chat-link handoff endpoint that allows attackers to bind an external chat identity to a victim's account. Attackers can craft a phishing page that auto-submits a POST request with a leaked confirmation token to bind their chat identity to a victim user's account, enabling impersonation within agent operations and inheritance of victim permissions.

Source published

Aug 13, 2026, 9:54:41 PM (timezone not stated)

Source modified

Oct 8, 2026, 3:24:34 PM (timezone not stated)

Observed here

9 Nov 2026 15:08:46 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 8.7 CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

Budibase before 3.40.0 contains a cross-site request forgery vulnerability in the chat-link handoff endpoint that allows attackers to bind an external chat identity to a victim's account. Attackers can craft a phishing page that auto-submits a POST request with a leaked confirmation token to bind their chat identity to a victim user's account, enabling impersonation within agent operations and inheritance of victim permissions.

Source published

13 Aug 2026 22:17:24 UTC

Source modified

8 Oct 2026 16:17:36 UTC

Observed here

25 Oct 2026 15:19:03 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 8.7 CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Secondary · 7.7 CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N

### Summary The Budibase AI chat-link handoff flow (`GET/POST /api/chat-links/:instance/:token/handoff`) binds an **external chat identity** (Slack/Discord/MS Teams/Telegram) to a **Budibase user account**. The confirmation endpoint is on a **public route** (no CSRF middleware, no auth-group gate) and the only credential it checks is a `confirmationToken` that is **already rendered in plaintext into the HTML confirmation page** the victim views. There is no binding between the confirmation token and the requester's Budibase session at preparation time, and no CSRF token on the POST. Consequently, an attacker who creates a chat-link session for **their own** external chat identity (or any identity they can mint in their chat platform) can induce a victim Budibase user (same tenant) to submit the confirmation POST -> for example by sending them a link that auto-submits, or by XSS/CSRF on a co-tenanted page -> and the victim's `globalUserId` becomes bound to the attacker's external identity. The attacker then sends messages to the AI agent from their chat platform and is **acting as the victim user** inside Budibase automations/agent operations, inheriting the victim's permissions on agent operations, knowledge sources, and any downstream automation steps keyed off the linked identity. --- ### Affected | Component | Path | Lines | |---|---|---| | Public handoff routes (no auth-group middleware) | `packages/server/src/api/routes/chat.ts` | `23` (`GET /api/chat-links/:instance/:token/handoff`), `27` (`POST .../handoff`) | | Confirmation controller | `packages/server/src/api/controllers/ai/chatIdentityLinks.ts` | `124-177` (`confirmChatLinkSession`); the binding at `153-173` | | Confirmation token rendered into HTML | `packages/server/src/api/controllers/ai/chatIdentityLinks.ts` | `40-60` (`renderLinkConfirmationPage`); the hidden input at `55` | | Session creation (attacker side) | `packages/server/src/sdk/workspace/ai/chatIdentityLinks.ts` | `138-171` (`createChatIdentityLinkSession`), `173-188` (`prepareChatIdentityLinkSessionConfirmation`) | | Upsert of identity link | `packages/server/src/sdk/workspace/ai/chatIdentityLinks.ts` | `201-250` (`upsertChatIdentityLink`) | **Affected versions:** `master` at commit `3c8d1b4023`. **Reachable over HTTP by:** the GET and POST are on `publicRoutes` (no auth-group middleware). The POST requires `ctx.isAuthenticated` at runtime (`controllers/ai/chatIdentityLinks.ts:142`) -> so the victim must be logged into Budibase when the POST fires (achievable via standard CSRF if cookies are sent cross-origin, or via phishing that lures the victim to submit). --- ### Root cause **Issue 1 -> The handoff routes are public and unauthenticated at the middleware layer.** ```ts // packages/server/src/api/routes/chat.ts:23, 27 publicRoutes.get("/api/chat-links/:instance/:token/handoff", ai.handoffChatLinkSession) publicRoutes.post("/api/chat-links/:instance/:token/handoff", ai.confirmChatLinkSession) ``` `publicRoutes` has **no group middleware** (`endpointGroups/standard.ts:24-25` calls `endpointGroupList.group()` with no middleware and then `.lockMiddleware()`). The routes do not have a per-route `authorized(...)`. There is **no CSRF middleware** on these routes -> Budibase's CSRF synchroniser token is enforced only for state-changing verbs on authenticated routes that are not in `NO_CSRF_ENDPOINTS`; the public-routes path bypasses it. **Issue 2 -> The confirmation token is exposed to anyone who views the GET page.** ```ts // packages/server/src/api/controllers/ai/chatIdentityLinks.ts:40-60 const renderLinkConfirmationPage = (session, action) => { ... return `<!doctype html>... <form method="post" action="${helpers.escapeHtml(action)}"> <input type="hidden" name="confirmationToken" value="${helpers.escapeHtml(session.confirmationToken)}"> <button type="submit">Confirm</button> </form> ...` } ``` The `confirmationToken` (a `newid()` UUIDv4 generated by `prepareChatIdentityLinkSessionConfirmation`) is rendered into a hidden form input. Anyone who loads the GET page sees the token in the page source. **Issue 3 -> The POST binds the **currently-authenticated user** to the external identity based solely on the confirmation token.** ```ts // packages/server/src/api/controllers/ai/chatIdentityLinks.ts:124-177 export async function confirmChatLinkSession(ctx) { ... if (!ctx.isAuthenticated) { throw new HTTPError("Authentication is required to link chat identity", 401) } if (!session.confirmationToken || ctx.request.body?.confirmationToken !== session.confirmationToken) { throw new HTTPError("Link confirmation is invalid or has expired", 400) } const currentGlobalUserId = getCurrentGlobalUserId(ctx) // <- victim's ID const consumedSession = await sdk.ai.chatIdentityLinks.consumeChatIdentityLinkSession(token) ... await sdk.ai.chatIdentityLinks.upsertChatIdentityLink({ provider: consumedSession.provider, externalUserId: consumedSession.externalUserId, // <- attacker's chat identity externalUserName: consumedSession.externalUserName, ... globalUserId: currentGlobalUserId, // <- bound to victim linkedBy: currentGlobalUserId, }) ... } ``` There is **no binding between the session and the requester's Budibase identity at preparation time**. `prepareChatIdentityLinkSessionConfirmation` (`sdk/workspace/ai/chatIdentityLinks.ts:173-188`) stores the `confirmationToken` keyed by `token` with no user-id field. Whoever is authenticated when the POST fires (and supplies the correct `confirmationToken`) gets bound. **Issue 4 -> `assertSessionMatchesInstance` only checks workspace ID, not user.** ```ts // packages/server/src/api/controllers/ai/chatIdentityLinks.ts:17-27 const assertSessionMatchesInstance = ({ workspaceId, instance }) => { if (!workspaceId || workspaceId !== instance) { throw new HTTPError("Link token is not valid for this workspace", 400) } } ``` The check confirms the session belongs to the same workspace as the URL `instance` param -> useful for preventing cross-workspace confusion but useless against same-tenant identity confusion. --- ### Reproduction **Step-by-step attack** 1. **Attacker (tenant T) provisions a chat-link session for their own external identity.** Via the agent channel provisioning flow (e.g. `POST /api/agent/:agentId/slack/provision` or via the Discord/MS Teams/Telegram provisioning endpoints), the attacker obtains a chat-link `token` bound to **their own** Slack user ID. The session is stored in Redis keyed by `token`, scoped to tenant T. 2. **Attacker triggers `prepareChatIdentityLinkSessionConfirmation`.** Either by GETting the handoff page themselves (if they have a Budibase session) or via an internal API. The `confirmationToken` is generated and stored. 3. **Attacker crafts a phishing/auto-submit page** that POSTs to `/api/chat-links/<instance>/<token>/handoff` with the leaked `confirmationToken` in the body. Example: ```html <form id="f" method="post" action="https://victim.budibase.app/api/chat-links/app_xxx/linktoken/handoff"> <input name="confirmationToken" value="<leaked-token>"> </form> <script>document.getElementById('f').submit()</script> ``` 4. **Victim (a Budibase user in tenant T, e.g. an admin) is lured to the attacker page** while logged into Budibase. Their browser sends the POST cross-origin. If the Budibase auth cookie is sent on cross-site requests (`SameSite=Lax` by default allows top-level POST navigations, which a form-submit is), the request is authenticated as the victim. 5. **The victim's `globalUserId` is now bound to the attacker's Slack identity.** When the attacker DMs the AI agent from Slack, the agent's operations run as the victim user -> with the victim's permissions on agent operations, knowledge sources, file uploads, and any downstream automation steps keyed off the linked identity. **Mitigating factors:** - `SameSite=Lax` cookies block cross-site POSTs from sub-resources (fetch / XHR) but **allow** top-level form-POST navigations. A phishing page that submits the form via `document.form.submit()` (a top-level navigation) succeeds. So the CSRF works with the default cookie policy. - The attack is **same-tenant only** (`session.tenantId !== context.getTenantId()` is checked in the sdk). - The attacker must induce the victim to click a link (standard phishing). No silent drive-by. --- ### Impact | Capability | Available | |---|---| | Bind an attacker-controlled chat identity to a victim's Budibase account | ✅ | | Send messages to the AI agent as the victim user (Slack/Discord/MS Teams/Telegram) | ✅ | | Inherit the victim's permissions on agent operations | ✅ | | Trigger automations / agent operations that the victim is authorised for | ✅ | | Read knowledge sources the victim has access to | ✅ | The severity depends on what the agent can do as the victim. For an admin victim, this is full tenant administration via chat. For a regular user, it is impersonation within the agent subsystem. The bound identity persists until manually unlinked, so the attacker retains ongoing access. This is a same-tenant, user-interaction-required primitive. It is below the "unauthenticated RCE" threshold but above "hardening" -> it is a real authentication-confusion vulnerability on a sensitive identity-binding operation. --- ### Fix **Recommended layered fixes:** 1. **Bind the confirmation token to the requester's Budibase session at preparation time.** In `prepareChatIdentityLinkSessionConfirmation`, store the `globalUserId` of the requester alongside the `confirmationToken`. In `confirmChatLinkSession`, verify that `getCurrentGlobalUserId(ctx)` matches the stored requester. This breaks the CSRF / cross-user confusion. 2. **Add a CSRF token to the confirmation POST.** The standard Budibase CSRF synchroniser token (`x-csrf-token` header, validated against the session's `csrfToken`) should be enforced on `POST /api/chat-links/.../handoff`. Move the route out of `publicRoutes` to an authenticated route group so CSRF applies (the GET can remain public for the redirect-to-login flow; the POST should be authenticated + CSRF-protected). 3. **Add a per-session nonce that is bound to the requester's browser** (e.g. a signed cookie set on the GET, validated on the POST) to prevent cross-origin submission even when `SameSite=Lax` allows it. 4. **Require user re-authentication (re-entry of password / step-up auth)** for sensitive identity-binding operations, similar to how password change requires re-auth.

Source published

24 Jul 2026 21:42:51 UTC

Source modified

14 Aug 2026 04:12:08 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N

Publisher rating · HIGH