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

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Vitest is a testing framework powered by Vite. Prior to 3.2.5 and 4.1.0, the Vitest UI/API server on Windows used isFileServingAllowed incorrectly for /__vitest_attachment__, allowing \\?\\..\\ path traversal to read files outside the project; exposed API write and rerun features such as saveTestFile and rerun could also allow arbitrary script execution. This issue is fixed in versions 3.2.5 and 4.1.0.

Source published

14 Jul 2026 19:28:08 UTC

Source modified

21 Jul 2026 15:02:17 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Vitest is a testing framework powered by Vite. Prior to 3.2.5 and 4.1.0, the Vitest UI/API server on Windows used isFileServingAllowed incorrectly for /__vitest_attachment__, allowing \\?\\..\\ path traversal to read files outside the project; exposed API write and rerun features such as saveTestFile and rerun could also allow arbitrary script execution. This issue is fixed in versions 3.2.5 and 4.1.0.

Source published

14 Jul 2026 20:17:02 UTC

Source modified

24 Oct 2026 21:10:00 UTC

Observed here

25 Oct 2026 12:17:26 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS 3.1 · [email protected] · Primary · 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

### 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/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. - https://github.com/vitest-dev/vitest/blob/eb1abf08573032a532015b999ad3501c5e89e3bb/packages/vitest/src/api/setup.ts#L103-L105 - https://github.com/vitest-dev/vitest/blob/eb1abf08573032a532015b999ad3501c5e89e3bb/packages/vitest/src/api/setup.ts#L119-L121 - https://github.com/vitest-dev/vitest/blob/eb1abf08573032a532015b999ad3501c5e89e3bb/packages/browser/src/node/commands/fs.ts#L10-L11 - https://github.com/vitest-dev/vitest/blob/eb1abf08573032a532015b999ad3501c5e89e3bb/packages/browser/src/node/plugin.ts#L194-L196 - https://github.com/vitest-dev/vitest/blob/eb1abf08573032a532015b999ad3501c5e89e3bb/packages/browser/src/node/rpc.ts#L115-L121 **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&contentType=text/plain&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`](https://vitest.dev/config/api.html#api-allowwrite) and [`allowExec`](https://vitest.dev/config/api.html#api-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`](https://vitest.dev/config/browser/api.html#api-allowwrite). Users who require the full interactive UI on a networked host must explicitly opt in by setting `allowWrite` and/or `allowExec` to `true`.

Source published

1 Jun 2026 14:09:53 UTC

Source modified

10 Sep 2026 03:50:48 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Publisher rating · CRITICAL