CVE-2026-33806

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

Published Apr 15, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-247c-9743-5963 Fastify has a Body Schema Validation Bypass via Leading Space in Content-Type Header
History
Type Values Removed Values Added
CPEs cpe:2.3:a:fastify:fastify:*:*:*:*:*:node.js:*:*
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Fastify
Fastify fastify
Vendors & Products Fastify
Fastify fastify
Type Values Removed Values Added
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.
Title fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header
Weaknesses CWE-1287
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
openjs
Published
Updated
Jul 15, 2026, 1:06 AM
Reserved
Mar 23, 2026, 7:48 PM
Status
Modified
Published
Apr 15, 2026, 4:17 AM
Modified
Jul 15, 2026, 2:20 AM
Severity
Important
Public date
Apr 15, 2026, 12:14 AM