GHSA-xh87-mx6m-69f3
Hono is Vulnerable to Authentication Bypass by IP Spoofing in AWS Lambda ALB conninfo
Packages
Details
As written in the advisory (Markdown source, shown as plain text).
## 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:
```ts
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:
```ts
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
External links from the advisory. They lead to third-party sites.