Vite: First 4 bytes of files outside of `server.fs` setting is exposed by `?vite-wasm-instance`
Published Oct 20, 2026 · Updated Nov 3, 2026
Original summary
Normalized public record · Updated Nov 3, 2026
Vite: First 4 bytes of files outside of `server.fs` setting is exposed by `?vite-wasm-instance`
Publisher and source text is retained separately from QFinch interpretation.
QFinch assessment
The first 4 bytes of files outside of server.fs setting can be returned to the browser by a request containing ?vite-wasm-instance.
Potential impact
Only apps that match one of the following conditions are affected: - explicitly expose the Vite dev server to the network using --host or the server.host option - there's a file that has a sensitive information in the first 4 bytes - uses Node.js or Deno to run Vite (if Bun is used, it is not affected)
Technical context
Requests containing the ?vite-wasm-instance query are handled by the internal Wasm plugin's load hook. The hook removes the query and reads the resulting path directly from disk, but the server.fs checks were not applied. After reading the file, Vite attempts to parse it as WebAssembly. When that parse fails, Node and deno throws an error that contains the first 4 bytes of the file.
Evidence: public source recordsAffected products
| Affected package, product or range | Fix status |
|---|---|
| Consult the referenced vendor advisory for affected versions. | Consult source advisory |
Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.
Remediation
Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.
- Confirm the affected product and reachable code path exist in your environment.
- Apply the vendor-supported patch or mitigation from the primary advisory.
- Rescan the exact deployed revision and retain verification evidence.
Evidence coverage
- SSVC priority
- LOW
- Confidence
- Not available
- Aliases
- None reported
Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.
Sources and record history
Record history
Published Oct 20, 2026 · Last refreshed Nov 3, 2026