CVE-2026-33221: Nhost Storage Affected by MIME Type Spoofing via Trusted Client Content-Type Header in Storage Upload
Vulnerability summary
CVE-2026-33221 is a medium (CVSS 5.3) vulnerability in nhost. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 7.5% of scored vulnerabilities.
Not severe (CVSS 2.1, network access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 2 · Related 2Timeline
- 20-03-2026PublishedVulnerability first disclosed.
- 25-03-2026Last modifiedVulnerability information updated.
Description
Nhost is an open source Firebase alternative with GraphQL. Prior to version 0.12.0, 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. This issue has been patched in version 0.12.0.
CVSS metrics
5 scores · 3 sources · 2 versions- OSV · GoEcosystem advisory · calculated2.1LowCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
- NVDNIST2.1LowCVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
- OSV · GoEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS trend
Probability
0.18%
Chance of exploitation in the next 30 days
Percentile
8%
Versus all other CVEs
30-day change
Decrease -0.02 pp
From 0.20% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-343Predictable Value Range from Previous ValuesThe product's random number generator produces a series of values which, when observed, can be used to infer a relatively small range of possibilities for the next value that could be generated.
- CWE-345Insufficient Verification of Data AuthenticityThe product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.
Affected systems
Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.
Github.com/nhost1 product
- nhost< 0.0.0-20260318074820-c4bd53f042d7
2 vendors · 3 products
References
7 links- github.com/nhost/nhost/security/advisories/GHSA-g9f6-9775-hffmX Refsource CONFIRMWEBAdvisoryMitigationVendor Advisory
- github.com/nhost/nhostPACKAGE