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CVE-2026-33806

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

Published: Apr 15, 2026Updated: Apr 17, 2026 Sources: CVE List NVDCWE-1287
NVD MITRE
7.5CVSSHIGH
EPSS Score
0.3%
Top 73.8%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

Impact: 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.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:NI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:NConfidentiality
None
I:HIntegrity
High
A:NAvailability
None
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Weaknesses

CWE-1287

Affected Products

fastifyfastify
Library
OSS Libraries / web-framework
fastifyoss-projectOSS Librariesaka fastify/middie, fastify-multipart

Exploitability

Official Patch Available

References

https://github.com/fastify/fastify/security/advisories/GHSA-mg2h-6x62-wpwc
github.com
https://cna.openjsf.org/security-advisories.html
cna.openjsf.org

Timeline

Published
Apr 15, 2026
Last Updated
Apr 17, 2026

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