CVE-2026-59897

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

MEDIUM
5.3
CVSS Score
Published: July 8, 2026 at 04:06 PM UTC
Updated: October 25, 2026 at 05:10 PM UTC
2 products affected across 2 vendorsHonoHono

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Severity
MEDIUM5.3
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

4.3.3 ≤ v < 4.12.27
Affected range stops below 4.12.27, so it looks safe — our inference, not a vendor statement
Affected range stops below 4.12.27, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (3)

x_refsource_CONFIRMVendor Advisory
Source: cverecord
https://github.com/honojs/hono/security/advisories/GHSA-xgm2-5f3f-mvvc
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/honojs/hono/releases/tag/v4.12.27

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-348

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