fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header

MITRE NVD CVE.ORG JSON API Print: PDF PDF

Summary

CVECVE-2026-33806
StatePUBLISHED
Assigneropenjs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-15 04:17:36 UTC
Updated2026-04-17 15:49:28 UTC
DescriptionImpact: Fastify applications using schema.body.content for per-content-type body validation can have validation bypassed entirely by prepending a space to the Content-Type header. The body is still parsed correctly but schema validation is skipped. This is a regression introduced in fastify >= 5.3.2 by the fix for CVE-2025-32442 Patches: Upgrade to fastify v5.8.5 or later. Workarounds: None. Upgrade to the patched version.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ce714d77-add3-4f53-aff5-83d477b104bb

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS: 0.000610000 probability, percentile 0.189790000 (date 2026-04-20)

Problem Types: CWE-1287 | CWE-1287 CWE-1287: Improper Validation of Specified Type of Input

VersionSourceTypeScoreSeverityVector
3.1ce714d77-add3-4f53-aff5-83d477b104bbSecondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
3.1CNACVSS7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Fastify Fastify All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Fastify Fastify affected 5.3.2 5.8.5 semver Not specified
CNA Fastify Fastify unaffected 5.8.5 semver Not specified

References

ReferenceSourceLinkTags
cna.openjsf.org/security-advisories.html ce714d77-add3-4f53-aff5-83d477b104bb cna.openjsf.org Vendor Advisory
github.com/fastify/fastify/security/advisories/GHSA-mg2h-6x62-wpwc ce714d77-add3-4f53-aff5-83d477b104bb github.com Not Applicable
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: mcollina (en)

CNA: climba03003 (en)

CNA: jsumners (en)

CNA: UlisesGascon (en)

CNA: Vyntral (en)

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