# CVE-2026-84373 — vitest-dev vitest

> As of 2026-09-02, CVE-2026-84373 is a MEDIUM-severity vulnerability in vitest-dev vitest, CVSS v3.1 5.9, EPSS 0.3% (30.5th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-84373 as of 2026-09-02; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-09-02

## What is CVE-2026-84373?

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.

The record classifies CVE-2026-84373 under weakness class [CWE-22](https://intel.threadlinqs.com/cwe/CWE-22). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality. 2 affected-product entries are recorded, across 2 vendors, listed below. The identifier was first published 34 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 5.9 — MEDIUM (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **EPSS (FIRST):** 0.3% probability of exploitation in the next 30 days, higher than 30.5% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 4.2/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-09-01, last modified 2026-09-02

## Is CVE-2026-84373 being exploited?

It currently carries a trending score of 37 in the Threadlinqs vulnerability feed.

## Affected products and versions

- **vitest-dev**: vitest
- **@vitest**: mocker

## How to fix CVE-2026-84373

No vendor patch reference has been recorded for CVE-2026-84373 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-84373

No threat campaign in the Threadlinqs corpus currently references CVE-2026-84373, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-09-03. This product uses the NVD API but is not endorsed or certified by the NVD.

**Vendor advisory and patch**

- [github.com](https://github.com/vitest-dev/vitest/security/advisories/GHSA-82fw-gwwq-j7x9)

**Other references**

- [github.com](https://github.com/vitest-dev/vitest/pull/10972)
- [github.com (10974)](https://github.com/vitest-dev/vitest/pull/10974)
- [github.com (51edf2b072902aec6d30c90ebaafd8f121c6f9d8)](https://github.com/vitest-dev/vitest/commit/51edf2b072902aec6d30c90ebaafd8f121c6f9d8)
- [github.com (8ff9b9a9efca7c6cfd5243569440de8d7a33aec4)](https://github.com/vitest-dev/vitest/commit/8ff9b9a9efca7c6cfd5243569440de8d7a33aec4)
- [github.com (fe5a11d3ceac5ec10d6d7d21a46d4caca132c48f)](https://github.com/vitest-dev/vitest/commit/fe5a11d3ceac5ec10d6d7d21a46d4caca132c48f)

_Showing 6 of 8 recorded references._

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-84373
Full detection coverage and IOCs for threats exploiting CVE-2026-84373 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp