CVE-2026-27700: Hono

High severity, CVSS 7.5. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Hono Hono: from 4.12.0, before 4.12.2 (fixed in 4.12.2)

Published 2026-02-25. Last modified 2026-06-17.