fastify vulnerable to Body Schema Validation Bypass via Leading Space in Content-Type Header
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.4%
exploitation probability
0.4%top 67% of all CVEs
observed exploitation
nono source reports it
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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Affected products
fastify · fastifyReferences
https://access.redhat.com/security/cve/CVE-2026-33806https://bugzilla.redhat.com/show_bug.cgi?id=2458596https://cna.openjsf.org/security-advisories.htmlhttps://github.com/fastify/fastify/security/advisories/GHSA-mg2h-6x62-wpwchttps://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-33806.json