vite: `server.fs.deny` bypass on Windows alternate paths
The advisory, in context
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
--hostorserver.hostconfig 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
$ 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?rawreturns the contents of.env/tls.pem::$DATA?rawreturns the contents oftls.pem
Affected packages
Start with the recorded fix for your release branch. Check your installed version and test compatibility before upgrading. Fixing this advisory does not rule out other vulnerabilities in the release.
From 8.0.0 before 8.0.16
Fixed in 8.0.16
View affected-version evidence
{
"ranges": [
{
"events": [
{
"introduced": "8.0.0"
},
{
"fixed": "8.0.16"
}
],
"type": "SEMVER"
}
],
"versions": []
}From 7.0.0 before 7.3.5
Fixed in 7.3.5
View affected-version evidence
{
"ranges": [
{
"events": [
{
"introduced": "7.0.0"
},
{
"fixed": "7.3.5"
}
],
"type": "SEMVER"
}
],
"versions": []
}Earlier releases before 6.4.3
Fixed in 6.4.3
View affected-version evidence
{
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "6.4.3"
}
],
"type": "SEMVER"
}
],
"versions": []
}Earlier releases before 0.1.24
Fixed in 0.1.24
View affected-version evidence
{
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "0.1.24"
}
],
"type": "SEMVER"
}
],
"versions": []
}