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

February 25, 2026 (updated February 27, 2026)

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.

References

Code Behaviors & Features

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