CVE-2026-59897 Hono: API Gateway v1 adapter can drop a distinct repeated request header value during de-duplication
Attackers can cause incomplete header data processing in Hono's AWS API Gateway adapter, potentially bypassing security controls like rate limiting or audit logging.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-59897?
CVE-2026-59897 is a medium-severity vulnerability in honojs hono, published on 8 Jul 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. From 4.3.3 before 4.12.27, the AWS API Gateway v1 adapter can drop a distinct repeated request header value because it de-duplicates values using a substring comparison instead of an exact match, so middleware or application logic that depends on the complete X-Forwarded-For chain, rate limiting, audit logging, or proxy-chain validation can receive incomplete data. This issue is fixed in version 4.12.27.
Weakness: CWE-348
Which versions are affected by CVE-2026-59897?
2 open source packages ship an affected version, including hono. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
hono npm | From 4.3.3 | 4.12.27 |
hono npm | From 4.3.3 | 4.12.27 |
Products include Hono Hono.
How do I fix CVE-2026-59897?
Upgrade hono to 4.12.27 or later.
Is CVE-2026-59897 being exploited?
There is no known exploitation of CVE-2026-59897 in the wild and no public exploit code.
Other vulnerabilities in honojs hono
- CVE-2026-27700 Hono is Vulnerable to Authentication Bypass by IP Spoofing in AWS Lambda ALB conninfo
- CVE-2026-22817 JWT Algorithm Confusion via Unsafe Default (HS256) in Hono JWT Middleware Allows Token Forgery and Auth Bypass
- CVE-2026-22818 JWT algorithm confusion in Hono JWK Auth Middleware when JWK lacks "alg" (untrusted header.alg fallback)
- CVE-2025-62610 Hono Improperly Authorizes JWT Audience Validation
- CVE-2026-29045 Hono: Arbitrary file access via serveStatic vulnerability
Sources
Also known as CLEANSTART-2026-AS71906, ECHO-f0d8-e683-de6b, GHSA-xgm2-5f3f-mvvc, MINI-4w55-6rq5-g7jw, MINI-53q4-5p3c-hhhw, MINI-5mp4-7c39-59j6 and 8 more.