What’s Vulnerable › Vulnerabilities

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

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-07-08 · updated 2026-10-25
• Weakness: CWE-348

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 products

• honojs hono: from 4.3.3 before 4.12.27 — fixed in 4.12.27

How to fix

Upgrade to a fixed version: honojs hono 4.12.27. Check the vendor advisory for mitigations.

References

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

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