Vulnerability · Published Jul 8, 2026 · Assigned by GitHub_M

CVE-2026-59897Hono: API Gateway v1 adapter can drop a distinct repeated request header value during de-duplication

Medium 4.8

In plain English

A medium-severity security flaw in hono from honojs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 8% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)4.8Medium

Exploit odds (30 days)0.2%top 92.4% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	hono	4.12.27	GHSA-xgm2-5f3f-mvvc

Affected products (as reported)

Vendor	Product	Versions
honojs	hono	>= 4.3.3, < 4.12.27

Weakness: CWE-348 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

References

https://github.com/honojs/hono/security/advisories/GHSA-xgm2-5f3f-mvvc x_refsource_CONFIRM
https://github.com/honojs/hono/commit/aa921770d09bc35970362d5a2630a878f6d982fd x_refsource_MISC
https://github.com/honojs/hono/releases/tag/v4.12.27 x_refsource_MISC