CVE-2026-33806

HIGH 7.5

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

CVSS Score

7.5

EPSS Score

0.0%

EPSS Percentile

13th

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.

CWE	CWE-1287
Vendor	fastify
Product	fastify
Published	Apr 15, 2026
Last Updated	Apr 15, 2026

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CVSS v3 Breakdown

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

Attack Vector

Attack Complexity

Privileges Required

User Interaction

Scope

Confidentiality

Integrity

Availability

Affected Versions

fastify / fastify

5.3.2 < 5.8.5

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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

Credits

mcollina climba03003 jsumners UlisesGascon 🔍 Vyntral