Summary
When using the AWS Lambda adapter (hono/aws-lambda) behind an Application Load Balancer (ALB), the getConnInfo() function incorrectly selected the first value from the X-Forwarded-For header.
Because AWS ALB appends the real client IP address to the end of the X-Forwarded-For header, the first value can be attacker-controlled.
This could allow IP-based access control mechanisms (such as the ipRestriction middleware) to be bypassed.
Details
In ALB environments, AWS appends the actual client IP address to the end of any existing X-Forwarded-For header value. However, the previous implementation of getConnInfo() extracted the leftmost IP address:
address = xff.split(',')[0].trim()If a client sent:
X-Forwarded-For: <spoofed-ip>
ALB would forward:
X-Forwarded-For: <spoofed-ip>, <real-client-ip>
Since the implementation selected the first value, the spoofed IP address was trusted. This affected applications using:
ipRestriction(getConnInfo, { allowList: [...] })or any custom middleware relying on getConnInfo(c).remote.address for authorization decisions.
The issue only affects deployments using the AWS Lambda adapter behind an ALB. API Gateway (v1/v2) and Lambda Function URLs are not affected, as they use AWS-provided source IP values from requestContext.
Impact
An unauthenticated remote attacker could bypass IP-based access restrictions by supplying a crafted X-Forwarded-For header. This may allow access to resources that were intended to be restricted by IP address.
Only applications deployed behind an ALB and relying on getConnInfo() for IP-based authorization are affected.
References
EdamAme-x Reporter
Summary
When using the AWS Lambda adapter (
hono/aws-lambda) behind an Application Load Balancer (ALB), thegetConnInfo()function incorrectly selected the first value from theX-Forwarded-Forheader.Because AWS ALB appends the real client IP address to the end of the
X-Forwarded-Forheader, the first value can be attacker-controlled.This could allow IP-based access control mechanisms (such as the
ipRestrictionmiddleware) to be bypassed.Details
In ALB environments, AWS appends the actual client IP address to the end of any existing
X-Forwarded-Forheader value. However, the previous implementation ofgetConnInfo()extracted the leftmost IP address:If a client sent:
ALB would forward:
Since the implementation selected the first value, the spoofed IP address was trusted. This affected applications using:
or any custom middleware relying on
getConnInfo(c).remote.addressfor authorization decisions.The issue only affects deployments using the AWS Lambda adapter behind an ALB. API Gateway (v1/v2) and Lambda Function URLs are not affected, as they use AWS-provided source IP values from
requestContext.Impact
An unauthenticated remote attacker could bypass IP-based access restrictions by supplying a crafted
X-Forwarded-Forheader. This may allow access to resources that were intended to be restricted by IP address.Only applications deployed behind an ALB and relying on
getConnInfo()for IP-based authorization are affected.References