Intel

AIKIDO-2026-132102

@fastify/aws-lambda is vulnerable to Authentication Bypass

CVE-2026-18248Published Aug 4, 2026
August 4, 2026

91

CVE Score

Critical

Authentication Bypass

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TL;DR

The request.awsLambda decoration, which exposes event and context for handlers that read API Gateway authorizer claims, resolves those values from the client-controlled x-apigateway-event and x-apigateway-context headers before falling back to the internal per-invocation token, and those reserved headers are not stripped from the incoming proxy event. An unauthenticated caller who can set a single HTTP header can therefore forge the entire Lambda event, including requestContext.authorizer, and override the genuine one. Any application that trusts request.awsLambda.event for identity or access control can be fully authentication- and authorization-bypassed. The fix resolves the decoration only through the internal token map and strips the reserved headers before the request is injected.

How do I fix this?

Upgrade the @fastify/aws-lambda library to the patch version.

Who does this affect?

You are affected if you are using a version that falls within the vulnerable range and your application trusts request.awsLambda.event or request.awsLambda.context for authentication or authorization decisions.

Versions

6.4.0 - 6.4.0

Fixed in 6.4.1

Background info

@fastify/aws-lambda is vulnerable to Authentication Bypass in versions 6.4.0 - 6.4.0.

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