CVE-2026-27700 HIGH

CVE-2026-27700: Hono is Vulnerable to Authentication Bypass by IP Spoofing in AWS Lambda ALB conninfo

Vendor Honojs
Product hono
Weakness CWE-345
Published February 25, 2026
Last update February 27, 2026

CVSS base score

8.2/10
Attack vector Network
Attack complexity Low
Privileges required None
User interaction None
Confidentiality High
Integrity Low

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

What the vulnerability does

01Description

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.

Key dates

02Disclosure timeline

February 25, 2026 CVE published
February 27, 2026 Record updated