CVE-2026-33806

HIGH7.5

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

Published Apr 15, 2026

Modified 1 months ago

Details

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.

References

WEB

https://cna.openjsf.org/security-advisories.html

WEB

https://github.com/fastify/fastify/security/advisories/GHSA-mg2h-6x62-wpwc

ADVISORY

https://www.cve.org/CVERecord?id=CVE-2026-33806

CVSS Analysis

CVSS v3.1

7.5

Exploitability

Attack Vector

NetworkAV:N

Attack Complexity

LowAC:L

Privileges Required

NonePR:N

User Interaction

NoneUI:N

Scope

UnchangedS:U

Impact

Confidentiality

NoneC:N

Integrity

HighI:H

Availability

NoneA:N

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

Weakness Type (CWE)

Other

CWE-1287

Ecosystems

Timeline

PublishedApr 15, 2026

ModifiedApr 15, 2026