Fastify
CVE-2026-25223
HIGH
GHSA-jx2c-rxcm-jvmq
Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata – not a confirmed exploit chain
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AccessCraft HTTP request with malicious Content-Type header
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ExploitAppend tab character and arbitrary content
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ExecutionBypass body validation schema
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ImpactProcess request with unvalidated payload
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A06:2025 - Insecure Design
ASVS 5.0
V4 - API and Web Service Interpretation consistency
|
| Exploitation Conditions | Fastify versions prior to 5.7.2 with request body validation schemas enabled. Attacker sends Content-Type header with tab character (\t) appended to valid content type, bypassing validation while server processes original content type. |
| Impact | CVSS 7.5 (HIGH). Attack vector: Network. Complexity: Low. Privileges required: None. User interaction: None. |
| Exploit ScenarioDerived | An attacker could exploit this vulnerability to compromise the affected system. |
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Alert meAnalysisAIv1 – Mar 12, 2026
Fastify versions before 5.7.2 allow attackers to bypass request body validation by injecting a tab character into the Content-Type header, enabling malicious payloads to reach application logic without validation checks. This remote attack requires no authentication and affects Node.js applications using vulnerable Fastify versions. A patch is available in version 5.7.2 and later.
Earlier versions of this analysis (1)
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. [CVSS 7.5 HIGH]
RemediationAI
A vendor patch is available — apply it immediately. Fixed in version 5.7.2.. Restrict network access to the affected service where possible.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in npm
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
Classified as CWE-436 (Interpretation Conflict). Affects Fastify. 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.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Primary rating from Vendor (github).
CVSS VectorVendor: github
Lifecycle Timeline
2DescriptionCVE.org
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.
Executive ViewAI
Fastify versions prior to 5.7.2 contain a validation bypass vulnerability that allows attackers to circumvent request body validation controls, potentially enabling injection attacks, data corruption, or unauthorized actions. Organizations using affected Fastify versions in production environments face immediate risk of exploitation if exposed to untrusted input.
Apply vendor patch. If immediate patching is not feasible: implement WAF rules to enforce strict Content-Type validation; add API gateway validation layer upstream of Fastify applications; restrict API access to known trusted sources via network segmentation; disable or restrict endpoints that accept user-supplied request bodies until patching is complete.
Threat Intelligence Overview
NVD
CVE.org
EPSS
VulDB
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Attack Technique
Authentication bypass attacks exploit flaws in the verification mechanisms that control access to systems and applications.
Affected Products (CPE)CVE.org
All versions of @fastify/oauth2 used a statically generated state parameter at startup time and were used across all req
A redirect vulnerability in the `fastify-static` module version >= 4.2.4 and < 4.4.1 allows remote attackers to redirect
Fastify is a fast and low overhead web framework, for Node.js. Rated high severity (CVSS 7.5), this vulnerability is rem
Prototype pollution vulnerability in fastify-multipart < 1.0.5 allows an attacker to crash fastify applications parsing
Fastify node module before 0.38.0 is vulnerable to a denial-of-service attack by sending a request with "Content-Type: a
A denial of service vulnerability exists in Fastify v2.14.1 and v3.0.0-rc.4 that allows a malicious user to trigger reso
A redirect vulnerability in the fastify-static module version < 4.2.4 allows remote attackers to redirect users to arbit
Authorization bypass in the @fastify/express middleware-compatibility plugin (versions 4.0.6 and earlier) lets unauthent
Authentication bypass in @fastify/express v4.0.4 and earlier allows remote unauthenticated attackers to access protected
Middleware bypass in Fastify Express plugin (fastify/express) allows complete circumvention of authentication, authoriza
Fastify is a web framework with minimal overhead and plugin architecture. Rated high severity (CVSS 8.8), this vulnerabi
Authentication and authorization bypass in @fastify/middie (Node.js middleware library for Fastify) allows remote unauth
Exploit-DB