CVE-2026-53571: Vite: `server.fs.deny` bypass on Windows alternate paths
Summary
The contents of files that are specified by server.fs.deny can be returned to the browser on Windows.
Impact
Only apps that match the following conditions are affected:
- explicitly exposes the Vite dev server to the network (using --host or server.host config option) - the sensitive file exists in the allowed directories specified by server.fs.allow - either of: - the sensitive file exists in an NTFS volume - the dev server is running on Windows and the sensitive file exists in a volume that 8.3 short name generation is enabled (it is enabled by default on system volumes)
Details
Vite’s dev server denies direct access to sensitive files through server.fs.deny, including entries such as .env, .env., and .{crt,pem}. However, on Windows, the deny logic does not correctly normalize NTFS ADS path forms before access checks are applied. Because of this, requests such as /.env::$DATA?raw are treated as allowed paths, while Windows resolves them to the original file's default data stream.
Similar to that, Windows allows accessing a file using a different name with the 8.3 short name compatibility feature. Vite did not reject accessing files via them.
PoC bash $ npm create vite@latest $ cd vite-project/ $ npm install $ npm run dev Access via browser at http://localhost:5173/.env::$DATA?raw <img width="388" height="129" alt="deecc1315123883cfd0f9c26a002845a" src="https://github.com/user-attachments/assets/895c6012-4e2e-4a35-babb-69bbf3ee7170" />
Example expected result: - /.env::$DATA?raw returns the contents of .env - /tls.pem::$DATA?raw returns the contents of tls.pem
Other sources
Vite is a frontend tooling framework for JavaScript. Prior to 8.0.16, 7.3.5, and 6.4.3, the contents of files that are specified by server.fs.deny can be returned to the browser on Windows. Vite’s dev server denies direct access to sensitive files through server.fs.deny, including entries such as .env, .env., and .{crt,pem}. However, on Windows, the deny logic does not correctly normalize NTFS ADS path forms before access checks are applied. Because of this, requests such as /.env::$DATA?raw are treated as allowed paths, while Windows resolves them to the original file's default data stream. Similar to that, Windows allows accessing a file using a different name with the 8.3 short name compatibility feature. Vite did not reject accessing files via them. This vulnerability is fixed in 8.0.16, 7.3.5, and 6.4.3.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
npm/vite-plusto a version that resolves this vulnerability.Fixed in 0.1.24 - Upgrade
Upgrade
npm/viteto a version that resolves this vulnerability.Fixed in 6.4.3 - Upgrade
Upgrade
npm/viteto a version that resolves this vulnerability.Fixed in 7.3.5 - Upgrade
Upgrade
npm/viteto a version that resolves this vulnerability.Fixed in 8.0.16
Event History
Frequently Asked Questions
What is the severity level of CVE-2026-53571?
CVE-2026-53571 has a high severity level of 8.2.
What vulnerability does CVE-2026-53571 address?
CVE-2026-53571 addresses a bypass vulnerability related to `server.fs.deny` on Windows alternate paths.
What impact does CVE-2026-53571 have on applications?
CVE-2026-53571 allows the contents of files specified by `server.fs.deny` to be returned to the browser, affecting network-exposed Vite dev servers.
How can I mitigate CVE-2026-53571 in my application?
To mitigate CVE-2026-53571, ensure that your Vite dev server is not exposed to the network or utilize updated configurations to secure file access.
Which software is affected by CVE-2026-53571?
CVE-2026-53571 affects npm/vite, vitejs Vite Node.js, npm/vite-plus, and Voidzero Vite+ Node.js.