Use of Less Trusted Source in hono - CVE-2026-54289

Detailed vulnerability description

The vulnerability allows a remote attacker to gain access to sensitive data.

The vulnerability exists due to on AWS Lambda@Edge, CloudFront delivers a request header that appears more than once as several separate entries. The adapter writes each value with Headers.set instead of Headers.append, so every value overwrites the previous one and only the last reaches the application. Repeated request headers such as X-Forwarded-For, Forwarded, and Via are silently truncated to a single value. Request middleware sees only the last value of a repeated header instead of the full chain. For applications that base access control on the X-Forwarded-For chain, this can weaken or alter that decision; for auditing, hop history is lost. A remote attacker can trigger the use of a less trusted source to gain access to sensitive data.

How to mitigate CVE-2026-54289

Sources

• https://github.com/honojs/hono/security/advisories/GHSA-wgpf-jwqj-8h8p