EUVD-2026-273674

fkie_cve-2026-27700

Hono is a Web application framework that provides support for any JavaScript runtime. In versions 4.12.0 and 4.12.1, 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. Version 4.12.2 patches the issue.

GHSA-xh87-mx6m-69f3 — Hono is Vulnerable to Authentication Bypass by IP Spoofing in AWS Lambda ALB conninfo

Affected: npm: hono

## 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 ma…

Most recent entries from all

EUVD-2026-273674

fkie_cve-2026-27700

GHSA-xh87-mx6m-69f3 — Hono is Vulnerable to Authentication Bypass by IP Spoofing in AWS Lambda ALB conninfo