Threaticon
Toggle sidebar

You're viewing a limited, public preview. Log in for full access.

Log in User Guide
Log in Get started
Vulnerabilities CVE-2026-18248

CVE-2026-18248

Critical
Open
TLP:CLEAR

@fastify/aws-lambda vulnerable to Lambda event spoofing via client-controlled x-apigateway-event header

AI Analysis

No AI analysis yet.

Description

@fastify/aws-lambda version 6.4.0 decorates each Fastify request with request.awsLambda.event and request.awsLambda.context, values that applications are documented to use for authorization decisions such as reading API Gateway authorizer claims. In the default configuration, the getter that populates this decoration reads the client-controlled x-apigateway-event and x-apigateway-context HTTP headers before falling back to the trusted internal request token, and those reserved headers are not stripped from the incoming event. An unauthenticated attacker who can set a single HTTP header can therefore forge the entire Lambda proxy event, including the authorizer context, and override the genuine one. This results in a full authentication and authorization bypass and privilege escalation for any application that trusts request.awsLambda.event for identity or access control. Only version 6.4.0 is affected. Patches: upgrade to @fastify/aws-lambda 6.4.1, which resolves the decoration only through the internal per-invocation token and strips the reserved headers before the request is processed.

Details

CVSS Score
9.1
EPSS Score
0.22%

12.3th percentile

CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Confidence
90%
Published
Aug 3, 2026
Last Modified
Aug 3, 2026
No notes yet. Click "Add Note" to create the first analysis note.
No opinions yet. Be the first to assess this intelligence.
Leaving Threaticon

This link opens an external site that isn't part of the platform.