Bug 2498157 (CVE-2026-59897)

Summary: CVE-2026-59897 hono: Hono: Information disclosure due to incorrect header de-duplication in AWS API Gateway v1 adapter
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: abarbaro, alizardo, dschmidt, jchui, jhe, jlanda, jwong, kshier, ktsao, nboldt, oaljalju, omaciel, psrna, rjohnson, sdawley, simaishi, stcannon, teagle, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in Hono, a web application framework. The AWS API Gateway v1 adapter incorrectly de-duplicates repeated request header values using a substring comparison, rather than an exact match. This can lead to incomplete data being received by middleware or application logic that relies on the full X-Forwarded-For chain, rate limiting, audit logging, or proxy-chain validation. Consequently, this could result in information disclosure or the bypass of security controls.
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Description OSIDB Bzimport 2026-07-08 17:02:35 UTC
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.