Is CVE-2026-59897 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-59897?

CVE-2026-59897 has a CVSS v3 severity of MEDIUM (4.8).

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CVE-2026-59897

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.