CVE-2026-33806 | fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header

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.

Published: 2026-04-15 Last update: 2026-04-17 Assigner: ce714d77-add3-4f53-aff5-83d477b104bb Source: ce714d77-add3-4f53-aff5-83d477b104bb
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-33806 is rated Low Risk (39.5/100): CVSS High severity, with low exploitation likelihood (EPSS 0.35%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-33806

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.06% 0.35% +0.29%
2 2026-04-18 0.04% 0.06% +0.02%
3 2026-04-15 — 0.04% —

Full EPSS history (3 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-33806

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 ce714d77-add3-4f53-aff5-83d477b104bb

Weakness enumeration for CVE-2026-33806

GitHub Security Advisory for CVE-2026-33806

GHSA-247c-9743-5963 · Severity: high · Ecosystem: npm — Fastify has a Body Schema Validation Bypass via Leading Space in Content-Type Header

OS Trackers for CVE-2026-33806

vendor priority summary link
redhat high — https://access.redhat.com/security/cve/CVE-2026-33806

Affected software / configurations for CVE-2026-33806

Vendor Product Version Raw CPE
fastify fastify >= 5.3.2, < 5.8.5 cpe:2.3:a:fastify:fastify:*:*:*:*:*:node.js:*:*

References for CVE-2026-33806

cvelogic Threat Intelligence