GHSA-g9f6-9775-hffm
Nhost Storage Affected by MIME Type Spoofing via Trusted Client Content-Type Header in Storage Upload
Packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| Go | github.com/nhost/nhost | < 0.0.0-20260318074820-c4bd53f042d7 | 0.0.0-20260318074820-c4bd53f042d7 |
Details
As written in the advisory (Markdown source, shown as plain text).
## Summary
The storage service's file upload handler trusts the client-provided `Content-Type` header without performing server-side MIME type detection. This allows an attacker to upload files with an arbitrary MIME type, bypassing any MIME-type-based restrictions configured on storage buckets.
## Affected Component
- **Service**: `services/storage`
- **File**: `services/storage/controller/upload_files.go`
- **Function**: `getMultipartFile` (lines 48-70)
## Root Cause
In `getMultipartFile`, if the client provides a non-empty `Content-Type` header that isn't `application/octet-stream`, the function returns it as-is without performing content-based detection:
```go
contentType := file.header.Header.Get("Content-Type")
if contentType != "" && contentType != "application/octet-stream" {
return fileContent, contentType, nil // skip detection entirely
}
// mimetype.DetectReader only reached if client sends no Content-Type
// or sends application/octet-stream
mt, err := mimetype.DetectReader(fileContent)
```
## Impact
**Incorrect MIME type in file metadata.** The MIME type stored in file metadata reflects what the client claims rather than what the file actually contains. Any system consuming this metadata (browsers, CDNs, applications) may handle the file incorrectly based on the spoofed type.
## Suggested Fix
Always detect MIME type from file content using `mimetype.DetectReader`, ignoring the client-provided `Content-Type` header entirely.
References
External links from the advisory. They lead to third-party sites.
- https://github.com/nhost/nhost/security/advisories/GHSA-g9f6-9775-hffm
- https://nvd.nist.gov/vuln/detail/CVE-2026-33221
- https://github.com/nhost/nhost/pull/4018
- https://github.com/nhost/nhost/commit/c4bd53f042d7f568e567e18e2665af81660fce85
- https://github.com/nhost/nhost
- https://github.com/nhost/nhost/releases/tag/storage%400.12.0
- https://github.com/nhost/nhost/releases/tag/[email protected]