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High severity · published Apr 15, 2026
CVE-2026-33806
fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header
7.5
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 39% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FA
fastify · fastify
5.3.2 before 5.8.5 · source: vendor, NVD
Affected product
FA
fastify
fastify
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-33806
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-33806
Vendor Advisory
https://cna.openjsf.org/security-advisories.html
Not Applicable
https://github.com/fastify/fastify/security/advisories/GHSA-mg2h-6x62-wpwc
access.redhat.com
https://access.redhat.com/security/cve/CVE-2026-33806
bugzilla.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2458596
security.access.redhat.com
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33806.json
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