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Vulnerability · Published Feb 3, 2026 · Assigned by GitHub_M

CVE-2026-25223Fastify's Content-Type header tab character allows body validation bypass

High 7.5

In plain English

A high-severity security flaw in fastify from fastify. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.9% (higher than 59% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.5High
Exploit odds (30 days)0.9%top 41.3% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
npmfastify5.7.2GHSA-jx2c-rxcm-jvmq

Affected products (as reported)

VendorProductVersions
fastify fastify < 5.7.2

Weakness: CWE-436, CWE-179 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References