CVE-2026-59897: Hono API Gateway V1 Adapter Can Vulnerability

MODERATE
Advisory Identifier: GHSA-xgm2-5f3f-mvvc
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CVSS 4.8
CWE-348
Published
Advisory Summary

CVE-2026-59897 is a MODERATE (CVSS 4.8) api gateway v1 adapter can vulnerability (CWE-348: Use of Less Trusted Source) affecting Hono libraries in the npm ecosystem. The issue involves api gateway v1 adapter can drop a distinct repeated request header value during de-duplication. Remediation is available by upgrading affected packages to version 4.12.27.

CVE-2026-59897 at a Glance

CVE Identifier CVE-2026-59897
GHSA Identifier GHSA-xgm2-5f3f-mvvc
Severity MODERATE
CVSS v3.1 Base Score 4.8
CWE Classification CWE-348: Use of Less Trusted Source
Affected Product Hono
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 4.8

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability None (A:N)

How to Fix CVE-2026-59897

To remediate this vulnerability, upgrade all affected Hono dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

hono fixed: 4.12.27 
npm install hono@4.12.27
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls hono

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-59897, inspect your project dependencies using npm:

npm ls hono

Analyze the terminal output to locate any version of Hono in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.12.27), your application is affected.

Note: The npm ls hono command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-348: Use of Less Trusted Source, where the product has two different sources of the same data or information, but it uses the source that has less support for verification, is less trusted, or is less resistant to attack. In Hono, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary The AWS API Gateway v1 adapter can drop a distinct repeated request header value. When a header appears multiple times, the adapter de-duplicates values using a substring comparison instead of an exact match, so a value that is a substring of another value of the same header is omitted (for example, `203.0.113.1` is dropped when another value is `203.0.113.10`). ### Details A repeated request header carries an ordered list of values. Middleware or application logic that depends on the complete list — such as IP restriction that walks the `X-Forwarded-For` chain, rate limiting, audit logging, or proxy-chain validation — can therefore receive incomplete data that differs from what the client actually sent. This issue arises on deployments using the AWS API Gateway v1 adapter (the same pattern also affects the VPC Lattice adapter), for requests that contain the same header more than once. ### Impact An attacker can craft repeated header values so that one value is omitted before the application sees the request. Where a security or routing decision relies on the full chain, this can alter that decision. This affects applications deployed through Hono's AWS API Gateway v1 (or VPC Lattice) adapter that rely on the complete set of repeated request header values.

CVE-2026-59897 Affected Hono Versions

1 component(s)
Fixed Versions:
4.12.27
Product / Package Ecosystem Affected Versions Fixed Version
hono
npm/hono
npm
≥ 4.3.3
< 4.12.27
4.12.27

References

GitHub Advisory / Wiki ADVISORY
https://github.com/honojs/hono/security/advisories/GHSA-xgm2-5f3f-mvvc
NVD — CVE-2026-59897 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-59897
Security Fix Commit FIX COMMIT
https://github.com/honojs/hono/commit/aa921770d09bc35970362d5a2630a878f6d982fd
Hono Source Repository REPOSITORY
https://github.com/honojs/hono
Hono Release RELEASE
https://github.com/honojs/hono/releases/tag/v4.12.27

Frequently Asked Questions

What is CVE-2026-59897?
CVE-2026-59897 is a security vulnerability in Hono involving API Gateway v1 adapter can drop a distinct repeated request header value during de-duplication under CWE-348: Use of Less Trusted Source.
Which Hono versions are affected?
Affected versions include releases prior to 4.12.27 across affected packages: hono.
What version fixes CVE-2026-59897?
Upgrading to 4.12.27 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hono affected?
Yes, hono is affected in releases prior to 4.12.27. Upgrade your dependency to 4.12.27 or later.
What is the CVSS score of CVE-2026-59897?
CVE-2026-59897 has a CVSS v3.1 base score of 4.8 (MODERATE) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.
What CWE is associated with CVE-2026-59897?
CVE-2026-59897 is classified under CWE-348: Use of Less Trusted Source (The product has two different sources of the same data or information, but it uses the source that has less support for verification, is less trusted, or is less resistant to attack.).
How can I check npm dependencies for CVE-2026-59897?
Run the dependency tree command: 'npm ls hono'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xgm2-5f3f-mvvc",
  "modified" : "2026-07-21T18:18:13Z",
  "published" : "2026-07-21T18:18:13Z",
  "aliases" : [ "CVE-2026-59897" ],
  "summary" : "Hono: API Gateway v1 adapter can drop a distinct repeated request header value during de-duplication",
  "details" : "### Summary\n\nThe AWS API Gateway v1 adapter can drop a distinct repeated request header value. When a header appears multiple times, the adapter de-duplicates values using a substring comparison instead of an exact match, so a value that is a substring of another value of the same header is omitted (for example, `203.0.113.1` is dropped when another value is `203.0.113.10`).\n\n### Details\n\nA repeated request header carries an ordered list of values. Middleware or application logic that depends on the complete list — such as IP restriction that walks the `X-Forwarded-For` chain, rate limiting, audit logging, or proxy-chain validation — can therefore receive incomplete data that differs from what the client actually sent.\n\nThis issue arises on deployments using the AWS API Gateway v1 adapter (the same pattern also affects the VPC Lattice adapter), for requests that contain the same header more than once.\n\n### Impact\n\nAn attacker can craft repeated header values so that one value is omitted before the application sees the request. Where a security or routing decision relies on the full chain, this can alter that decision.\n\nThis affects applications deployed through Hono's AWS API Gateway v1 (or VPC Lattice) adapter that rely on the complete set of repeated request header values.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.3.3"
      }, {
        "fixed" : "4.12.27"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/security/advisories/GHSA-xgm2-5f3f-mvvc"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-59897"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/commit/aa921770d09bc35970362d5a2630a878f6d982fd"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/honojs/hono"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/releases/tag/v4.12.27"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-348" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-21T18:18:13Z",
    "nvd_published_at" : "2026-07-08T17:17:27Z"
  }
}