CVE-2026-33806CWE-1287

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

High · published April 15, 2026

CVSS v3.1
7.5
EPSS
0%
Percentile
40.8
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
7.5 · HIGH
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
CVSS v4.0
Not supplied
EPSS
0.00485 · 40.8th percentile
Weakness
CWE-1287 · Improper Validation of Specified Type of Input
Published
2026-04-15T00:14Z
EPSS history
Timeline
  • 15 APR 00:14Z
    fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header
    cvelistv5