# CVE-2026-112950: Vitest: Windows backslash traversal bypasses the @vitest/mocker redirect allowlist fix


- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Fix available:** Yes
- **Published:** 20 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** CLSA-2026-1792617972, GHSA-xp26-3454-mjgp

## What is CVE-2026-112950?

CVE-2026-112950 is a medium-severity vulnerability in @vitest mocker, published on 20 Oct 2026. 

### Official description

Vitest is a Vite-native testing framework for JavaScript and TypeScript projects. From 4.1.11 until 4.1.12 and 5.0.3, isFileLoadingAllowed and the filesystem read interpret backslashes differently on Windows in packages/mocker/src/node/interceptorPlugin.ts. When a client can reach the Vite dev server on Windows and register a redirect mock containing backslash traversal, POSIX joining preserves a Windows backslash traversal that the later filesystem read interprets as a path separator, so the client can read a file outside server.fs.allow that the Vitest process can access. This issue is fixed in versions 4.1.12 and 5.0.3.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-112950?

4 open source packages ship an affected version, including @vitest/mocker.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `@vitest/mocker` | npm | From 4.1.11 | 4.1.12 |
| `@vitest/mocker` | npm | From 4.1.11 | 4.1.12 |
| `@vitest/mocker` | npm | From 5.0.0-rc.2 | 5.0.3 |
| `@vitest/mocker` | npm | From 5.0.0-rc.2 | 5.0.3 |

## How do I fix CVE-2026-112950?

Upgrade @vitest/mocker to a fixed version for your release line: 4.1.12 or 5.0.3.

## Is CVE-2026-112950 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-112950 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-112950 and fix it if it is affected.

What it is: CVE-2026-112950 is a medium-severity vulnerability in @vitest mocker, published on 20 Oct 2026. 
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-112950 exists.

Affected packages and fixed versions:
- @vitest/mocker (npm): affected from 4.1.11; fixed in 4.1.12
- @vitest/mocker (npm): affected from 4.1.11; fixed in 4.1.12
- @vitest/mocker (npm): affected from 5.0.0-rc.2; fixed in 5.0.3
- @vitest/mocker (npm): affected from 5.0.0-rc.2; fixed in 5.0.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-112950/ (Markdown: https://insights.sbomify.com/CVE-2026-112950/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-112950
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-112950
- OSV: https://osv.dev/vulnerability/CVE-2026-112950

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-112950/
Summaries are generated and may contain mistakes; the official description above is the record.