CVE Tools
Sign in

CVE-2026-6270

@fastify/middie vulnerable to middleware authentication bypass in child plugin scopes

Published: Apr 16, 2026Updated: May 14, 2026 Sources: CVE List NVDCWE-436
NVD MITRE
9.1CVSSCRITICAL
EPSS Score
0.5%
Top 61.3%
CISA KEV
Not in KEV
Exploits
No Known Exploits
Remediation
Patch Available

Description

@fastify/middie versions 9.3.1 and earlier do not register inherited middleware directly on child plugin engine instances. When a Fastify application registers authentication middleware in a parent scope and then registers child plugins with @fastify/middie, the child scope does not inherit the parent middleware. This allows unauthenticated requests to reach routes defined in child plugin scopes, bypassing authentication and authorization checks. Upgrade to @fastify/middie 9.3.2 to fix this issue. There are no workarounds.

CVSS Vector Breakdown

AV:NAC:LPR:NUI:NS:UC:HI:HA:N
Exploitability
AV:NAttack Vector
Network
AC:LAttack Complexity
Low
PR:NPrivileges Required
None
UI:NUser Interaction
None
Scope
S:UScope
Unchanged
Impact
C:HConfidentiality
High
I:HIntegrity
High
A:NAvailability
None
Open in CVSS calculator →

Weaknesses

CWE-436

Affected Products

@fastify/middie@fastify/middie
Library
OSS Libraries / web-framework
fastify\/middiefastify
Library
OSS Libraries / web-framework
@fastify/middieoss-projectUSOSS Librariesaka @fastify/middie, fastify-middie
fastifyoss-projectOSS Librariesaka fastify/middie, fastify-multipart

Exploitability

Official Patch Available
Workaround Available

References

https://github.com/fastify/fastify-express/security/advisories/GHSA-hrwm-hgmj-7p9c
github.com
https://github.com/fastify/middie/security/advisories/GHSA-72c6-fx6q-fr5w
github.com
https://cna.openjsf.org/security-advisories.html
cna.openjsf.org

Timeline

Published
Apr 16, 2026
Last Updated
May 14, 2026

Unlock Complete Vulnerability Intelligence

Get the full picture for CVE-2026-6270 and every CVE in our database. Create a free account — no credit card required.

Create Free Account
Plain-language analysis
Impact assessment and exploitation scenario in plain English
Attack graph visualization
Interactive attack path and kill chain mapping
Exploit details & PoC links
ExploitDB, Metasploit, GitHub PoCs with direct links
Nuclei scanner templates
Ready-to-use vulnerability scanner templates
Full remediation guide
Patch instructions, workarounds, and compliance impact
Interactive AI chat
Ask questions about this vulnerability in natural language
Related vulnerabilities
Semantically similar CVEs and attack patterns
REST API & MCP access
Integrate vulnerability data into your workflows