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CVE-2026-47429 — vitest

CRITICALFix: vitest-dev/vitest@20e00ef

CVE-2026-47429 is a critical-severity (CVSS 9.8) Path Traversal vulnerability in vitest. A fix is available for vitest — see the affected versions and patch details below.

Vitest: Arbitrary file can be read and executed when Vitest UI server is listening

Also known asGHSA-5xrq-8626-4rwp
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Oct 13, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

  • CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-47429.

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs58th percentile — riskier than 58% of all scored CVEsHighest risk
0.38%0.75%1.13%1.51%1.0%0.9%0.9%0.9%Aug 26Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2026-47429 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 386,684 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

2Kother npm packages depend on this — each one inherits the vulnerability until it's patched upstream
vitestnpm
125.8Mdownloads / week

Description

Summary

Arbitrary file can be read on Windows when Vitest UI server is listening, especially when exposed to the network.

Impact

Only users that match either of the following conditions are affected:

  • explicitly exposes the Vitest UI server to the network (using --api.host or api.host config option)
  • running the Vitest UI or Browser Mode on Windows

Details

The API handler for /__vitest_attachment__ uses the deprecated isFileServingAllowed incorrectly. https://github.com/vitest-dev/vitest/blob/eb1abf08573032a532015b999ad3501c5e89e3bb/packages/ui/node/index.ts#L77 The function expects the passed value to use cleanUrl after the check before file system related operation. Because of this, it is possible to bypass the check by \\?\\..\\. This is not possible on Linux as Linux errors if a directory named ? does not exist.

A similar problem exists in other places as well.

That said, this isFileServingAllowed check does not actually prevent the API to be abused. Since the API has rerun feature and file write feature, it's possible to run arbitrary script by writing a script as a test file using saveTestFile and running it using rerun. This means exposing the API / Vitest UI is equivalent to giving script execution access. On the browser mode side, there're readFile / writeFile / saveSnapshotFile. So exposing the browser mode is equivalent to giving file read / write access.

PoC

  1. Run Vitest UI
  2. Get the API token by curl http://localhost:51204/__vitest__/
  3. Run curl "http://localhost:51204/__vitest_attachment__?path=C:\\path\\to\\project\\?\\..\\..\\secret.txt&amp;contentType=text/plain&amp;token=$TOKEN" (TOKEN is the API token)
  4. curl shows the content of secret.txt that is outside the project directory

Mitigations

Vitest now ships two configuration flags, allowWrite and allowExec, that gate the privileged operations exploited by this vulnerability. Both are disabled by default whenever the API server is bound to a non-localhost host, ensuring that exposing the server to the network no longer implicitly grants write or execute capabilities to remote clients.

When these flags are disabled, the UI also enters a read-only mode: in-browser code editing and test file execution are turned off, removing the attack surface that allowed remote code execution. Many Browser Mode features are also disabled, like attachments, artifacts or snapshots. See browser.api.

Users who require the full interactive UI on a networked host must explicitly opt in by setting allowWrite and/or allowExec to true.

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
📦npmvitest≥ 4.0.0&&< 4.1.04.1.0npm install vitest@4.1.0
📦npmvitestall versions3.2.6npm install vitest@3.2.6

Affected Products

1 product · 2 configurations
Application
vitestvitest.dev
≥ 4.0.0 && < 4.1.0
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vitest, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update vitest to 4.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-47429 is resolved across your whole dependency graph.

  3. Workarounds

    Resolve every user-supplied path to its canonical form and reject anything that escapes the intended directory, and run the component under an account that has no read or write access outside the directory it legitimately serves.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Vitest ships a UI and API server (enabled via the --ui or --api flags, or automatically as part of Browser Mode) that exposes file read, file write, and test-rerun functionality over HTTP. Due to an incorrect path-traversal check in the /__vitest_attachment__ handler and related code paths, a remote attacker who can…

Workaround published by Red Hat
No mitigation is required for Red Hat products, as none run Vitest's UI/API server or Browser Mode in their build or shipped runtime. Developers who run `vitest --ui`, `vitest --api`, or Browser Mode interactively should avoid binding the server to a non-localhost host, and should upgrade to vitest >= 4.1.0 (or >= 3.2.5 on the 3.x branch), where the allowWrite/allowExec flags default to disabled whenever the server is bound to a non-localhost host.
Source: Red Hat security advisory for CVE-2026-47429 (CC BY 4.0)
ProductFixed inAdvisory
Red Hat Hardened Imagesprometheus3-13-main-3.13.1-0.1.hum1RHSA-2026:39058

Frequently Asked Questions

### Summary Arbitrary file can be read on Windows when Vitest UI server is listening, especially when exposed to the network. ### Impact Only users that match either of the following conditions are affected: - explicitly exposes the Vitest UI server to the network (using `--api.host` or [`api.host` config option](https://vitest.dev/config/api.html)) - running the Vitest UI or Browser Mode on Windows ### Details The API handler for `/__vitest_attachment__` uses the deprecated `isFileServingAllowed` incorrectly. https://github.com/vitest-dev/vitest/blob/eb1abf08573032a532015b999ad3501c5e89e3b
O3 Security · Impact-Aware SCA

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CVE-2026-47429: vitest RCE — Fixed in 4.1.0