CVE-2026-84364: Hono Unbounded Dot-notation Nesting Vulnerability

MODERATE
Advisory Identifier: GHSA-g6gw-c38x-mqfc
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CVSS 5.3
CWE-400
Published
Advisory Summary

CVE-2026-84364 is a MODERATE (CVSS 5.3) unbounded dot-notation nesting vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Hono libraries in the npm ecosystem. The issue involves unbounded dot-notation nesting in `parsebody()` can cause memory exhaustion. Remediation is available by upgrading affected packages to version 4.13.5.

CVE-2026-84364 at a Glance

CVE Identifier CVE-2026-84364
GHSA Identifier GHSA-g6gw-c38x-mqfc
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Hono
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 5.3

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

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

How to Fix CVE-2026-84364

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: 4.13.5 
npm install hono@4.13.5
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-2026-84364, 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 4.13.5), 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-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. 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 When `parseBody()` expands dot-separated form field names into nested objects, it does not limit the nesting depth or the total number of objects created. A request body well within a normal size limit can therefore allocate an object graph far larger than the request itself, and concurrent requests can exhaust the heap and terminate the process. ### Details Each dot-separated segment of a field name creates an intermediate object. Neither the segments within a single field name nor the total across a request was bounded, and empty segments were preserved, so a field name could encode one nesting level per byte. Both shapes produce the effect: a single deeply dotted field name, and a large number of shallowly dotted ones within one body. A request body size limit does not prevent it, because the amplification happens after the body has been accepted. Dot-notation parsing is not enabled by default. ### Impact An attacker who can reach an endpoint that parses request bodies with dot-notation enabled can send concurrent requests whose memory cost is disproportionate to their size. This may lead to: - exhaustion of the JavaScript heap and termination of the server process - the service remaining unavailable until it is restarted This issue affects applications that explicitly enable dot-notation parsing. Applications using the default behaviour are not affected.

CVE-2026-84364 Affected Hono Versions

1 component(s)
Fixed Versions:
4.13.5
Product / Package Ecosystem Affected Versions Fixed Version
hono
npm/hono
npm
< 4.13.5
4.13.5

References

GitHub Advisory / Wiki ADVISORY
https://github.com/honojs/hono/security/advisories/GHSA-g6gw-c38x-mqfc
NVD — CVE-2026-84364 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-84364
Security Fix Commit FIX COMMIT
https://github.com/honojs/hono/commit/531e9c5a3ae058d10de33f643055bd4009a87178
Hono Source Repository REPOSITORY
https://github.com/honojs/hono
Hono Release RELEASE
https://github.com/honojs/hono/releases/tag/v4.13.5

Frequently Asked Questions

What is CVE-2026-84364?
CVE-2026-84364 is a security vulnerability in Hono involving Unbounded dot-notation nesting in `parseBody()` can cause memory exhaustion under CWE-400: Uncontrolled Resource Consumption.
Which Hono versions are affected?
Affected versions include releases prior to 4.13.5 across affected packages: hono.
What version fixes CVE-2026-84364?
Upgrading to 4.13.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hono affected?
Yes, hono is affected in releases prior to 4.13.5. Upgrade your dependency to 4.13.5 or later.
What is the CVSS score of CVE-2026-84364?
CVE-2026-84364 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
What CWE is associated with CVE-2026-84364?
CVE-2026-84364 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check npm dependencies for CVE-2026-84364?
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-g6gw-c38x-mqfc",
  "modified" : "2026-09-08T21:23:02Z",
  "published" : "2026-09-08T21:23:02Z",
  "aliases" : [ "CVE-2026-84364" ],
  "summary" : "Hono: Unbounded dot-notation nesting in `parseBody()` can cause memory exhaustion",
  "details" : "### Summary\n\nWhen `parseBody()` expands dot-separated form field names into nested objects, it does not limit the nesting depth or the total number of objects created. A request body well within a normal size limit can therefore allocate an object graph far larger than the request itself, and concurrent requests can exhaust the heap and terminate the process.\n\n### Details\n\nEach dot-separated segment of a field name creates an intermediate object. Neither the segments within a single field name nor the total across a request was bounded, and empty segments were preserved, so a field name could encode one nesting level per byte.\n\nBoth shapes produce the effect: a single deeply dotted field name, and a large number of shallowly dotted ones within one body. A request body size limit does not prevent it, because the amplification happens after the body has been accepted.\n\nDot-notation parsing is not enabled by default.\n\n### Impact\n\nAn attacker who can reach an endpoint that parses request bodies with dot-notation enabled can send concurrent requests whose memory cost is disproportionate to their size.\n\nThis may lead to:\n\n- exhaustion of the JavaScript heap and termination of the server process\n- the service remaining unavailable until it is restarted\n\nThis issue affects applications that explicitly enable dot-notation parsing. Applications using the default behaviour are not affected.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.13.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/security/advisories/GHSA-g6gw-c38x-mqfc"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-84364"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/commit/531e9c5a3ae058d10de33f643055bd4009a87178"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/honojs/hono"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/releases/tag/v4.13.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-08T21:23:02Z",
    "nvd_published_at" : "2026-09-01T21:18:47Z"
  }
}