Vitest: Path Traversal / Arbitrary File Read via @vitest/mocker Redirect Mock

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.9 · CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-84373: 0.53% estimated exploitation activity in the next 30 days; percentile 44.71 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary @vitest/mocker registers a redirect mock's target path without validating it against the dev server's file-serving allowlist. An attacker who can reach the dev server's WebSocket can register a redirect mock pointing outside the project root; when the mocked module is requested, the plugin's load hook returns readFile(<attacker path) as the module source, disclosing local files. This is exploitable without authentication only through the public mockerPlugin / standalone interceptorPlugin exports (used by third-party dev servers), which register the handler on Vite's unauthenticated HMR socket. Vitest's own browser mode registers mocks over a token-authenticated RPC and is not remotely reachable by default (see Scope). Affected code packages/mocker/src/node/interceptorPlugin.ts. The load hook is the file-read sink: mock.redirect is derived from client input at registration time with no boundary check: There is no server.fs.allow / server.fs.deny check and no assertion that the…

Published by the source

8 Sep 2026, 20:46 UTC

Last modified by the source

8 Sep 2026, 21:00 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-82fw-gwwq-j7x9

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-82fw-gwwq-j7x9

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-82fw-gwwq-j7x9

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# Patch Next advisory brief: CVE-2026-84373

Advisory: Vitest: Path Traversal / Arbitrary File Read via @vitest/mocker Redirect Mock
IDs: CVE-2026-84373, GHSA-82fw-gwwq-j7x9
Record: https://patchnext.com/advisories/cve-2026-84373 (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @vitest/mocker 5.0.0-rc.2, 4.1.11; vitest 5.0.0-rc.2, 4.1.11. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @vitest/mocker: affected >= 2.1.0, < 4.1.11; >= 5.0.0-beta.1, < 5.0.0-rc.2; fixed in 5.0.0-rc.2, 4.1.11
- npm vitest: affected >= 2.1.0, < 4.1.11; >= 5.0.0-beta.1, < 5.0.0-rc.2; fixed in 5.0.0-rc.2, 4.1.11

## Suggested inspection (read-only)
- `npm ls @vitest/mocker --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls vitest --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @vitest/mocker, vitest.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-82fw-gwwq-j7x9 (GitHub-reviewed advisory GHSA-82fw-gwwq-j7x9 lists affected ranges: npm @vitest/mocker >=2.1.0 =5.0.0-beta.1 =2.1.0 =5.0.0-beta.1 <5.0.0-rc.2)
- Verified: https://osv.dev/vulnerability/GHSA-82fw-gwwq-j7x9 (OSV record GHSA-82fw-gwwq-j7x9 lists affected ranges: npm @vitest/mocker >=2.1.0 =5.0.0-beta.1 =2.1.0 =5.0.0-beta.1 <5.0.0-rc.2 (fixed))

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