Hono · Hono · CVE-2026-54289
**Name of the Vulnerable Software and Affected Versions**
Hono versions prior to 4.12.25
**Description**
On AWS Lambda@Edge, CloudFront delivers request headers that appear multiple times as separate entries. The adapter uses the `Headers.set` function instead of `Headers.append`, causing each subsequent value to overwrite the previous one, meaning only the final value reaches the application. This results in the silent truncation of repeated request headers such as `X-Forwarded-For`, `Forwarded`, and `Via` to a single value. Consequently, request middleware receives incomplete data instead of the full chain. For applications utilizing the `X-Forwarded-For` chain for access control, this can weaken or alter security decisions, and for auditing purposes, the hop history is lost.
**Recommendations**
Update to version 4.12.25.