# CVE-2026-54289: Hono: Lambda@Edge adapter keeps only the last value of a repeated request header, dropping the rest

> The Hono Lambda@Edge adapter truncates repeated request headers, potentially hiding IP chains and weakening access control decisions based on X-Forwarded-For.

- **Severity:** Medium 4.8 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 22 Jun 2026
- **Updated:** 22 Jun 2026
- **Also known as:** ECHO-d0c1-0187-7821, GHSA-wgpf-jwqj-8h8p, MINI-27rm-jq4x-vpqj, MINI-7627-xppq-r9r5, MINI-96hx-6pp7-fh57, MINI-c4c8-hjwq-4ccf, MINI-c4xv-qfgw-8xjq, MINI-j2cx-r843-f4f8, MINI-jjpj-9jvq-xj3r, MINI-p4w5-hp5r-gr3m, MINI-ppqg-mj4q-5p9g, MINI-q4qv-cqw5-c9w2, MINI-qgrv-m4ch-63rx, MINI-v693-h28g-qf77, ROOT-APP-NPM-CVE-2026-54289

## What is CVE-2026-54289?

CVE-2026-54289 is a medium-severity vulnerability in honojs hono, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.25, 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. This vulnerability is fixed in 4.12.25.

Weakness: CWE-348 (Use of Less Trusted Source)

## Which versions are affected by CVE-2026-54289?

2 open source packages ship an affected version, including hono.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `hono` | npm | All versions | 4.12.25 |
| `hono` | npm | All versions | 4.12.25 |

## How do I fix CVE-2026-54289?

Upgrade hono to 4.12.25 or later.

## Is CVE-2026-54289 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54289 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54289 and fix it if it is affected.

What it is: CVE-2026-54289 is a medium-severity vulnerability in honojs hono, published on 22 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54289 exists.

Affected packages and fixed versions:
- hono (npm): affected all versions; fixed in 4.12.25
- hono (npm): affected all versions; fixed in 4.12.25

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54289/ (Markdown: https://insights.sbomify.com/CVE-2026-54289/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54289
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54289
- OSV: https://osv.dev/vulnerability/CVE-2026-54289

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54289/
Summaries are generated and may contain mistakes; the official description above is the record.