Fastify's Content-Type header tab character allows body validation bypass
21Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 7.5epss 0.8%
exploitation probability
0.8%top 48% of all CVEs
observed exploitation
nono source reports it
Fastify is a fast and low overhead web framework, for Node.js. Prior to version 5.7.2, a validation bypass vulnerability exists in Fastify where request body validation schemas specified by Content-Type can be completely circumvented. By appending a tab character (\t) followed by arbitrary content to the Content-Type header, attackers can bypass body validation while the server still processes the body as the original content type. This issue has been patched in version 5.7.2.
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/errata/RHSA-2026:10184https://access.redhat.com/errata/RHSA-2026:5807https://access.redhat.com/errata/RHSA-2026:6192https://access.redhat.com/security/cve/CVE-2026-25223https://bugzilla.redhat.com/show_bug.cgi?id=2436560https://fastify.dev/docs/latest/Reference/Validation-and-Serializationhttps://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/content-type-parser.js#L125https://github.com/fastify/fastify/blob/759e9787b5669abf953068e42a17bffba7521348/lib/validation.js#L272https://github.com/fastify/fastify/commit/32d7b6add39ddf082d92579a58bea7018c5ac821https://github.com/fastify/fastify/security/advisories/GHSA-jx2c-rxcm-jvmqhttps://hackerone.com/reports/3464114https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-25223.json