CVE-2026-39409: Hono Hono Has Incorrect IP Matching Vulnerability

MODERATE
Advisory Identifier: GHSA-xpcf-pg52-r92g
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CVSS 5.3
CWE-180
Published
Advisory Summary

CVE-2026-39409 is a MODERATE (CVSS 5.3) hono has incorrect ip matching vulnerability (CWE-180: Incorrect Behavior Order: Validate Before Canonicalize) affecting Hono libraries in the npm ecosystem. The issue involves hono has incorrect ip matching in iprestriction() for ipv4-mapped ipv6 addresses. Remediation is available by upgrading affected packages to version 4.12.12.

CVE-2026-39409 at a Glance

CVE Identifier CVE-2026-39409
GHSA Identifier GHSA-xpcf-pg52-r92g
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-180: Incorrect Behavior Order: Validate Before Canonicalize
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:L/I:N/A:N).

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 Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-39409

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: 4.12.12 
npm install hono@4.12.12
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-2026-39409, 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 4.12.12), 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-180: Incorrect Behavior Order: Validate Before Canonicalize, where the product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step. 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 `ipRestriction()` does not canonicalize IPv4-mapped IPv6 client addresses (e.g. `::ffff:127.0.0.1`) before applying IPv4 allow or deny rules. In environments such as Node.js dual-stack, this can cause IPv4 rules to fail to match, leading to unintended authorization behavior. ## Details The middleware classifies client addresses based on their textual form. Addresses containing "`:`" are treated as IPv6, including IPv4-mapped IPv6 addresses such as `::ffff:127.0.0.1`. These addresses are not normalized to IPv4 before matching. As a result: * IPv4 static rules (e.g. `127.0.0.1`) do not match because the raw string differs * IPv4 CIDR rules (e.g. `127.0.0.0/8`, `10.0.0.0/8`) are skipped because the address is treated as IPv6 For example, with: `denyList: ['127.0.0.1']` a request from `127.0.0.1` may be represented as `::ffff:127.0.0.1` and bypass the deny rule. This behavior commonly occurs in Node.js environments where IPv4 clients are exposed as IPv4-mapped IPv6 addresses. ## Impact Applications that rely on IPv4-based `ipRestriction()` rules may incorrectly allow or deny requests. In affected deployments, a denied IPv4 client may bypass access restrictions. Conversely, legitimate clients may be rejected when using IPv4 allow lists.

CVE-2026-39409 Affected Hono Versions

1 component(s)
Fixed Versions:
4.12.12
Product / Package Ecosystem Affected Versions Fixed Version
hono
npm/hono
npm
< 4.12.12
4.12.12

References

GitHub Advisory / Wiki ADVISORY
https://github.com/honojs/hono/security/advisories/GHSA-xpcf-pg52-r92g
NVD — CVE-2026-39409 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39409
Security Fix Commit FIX COMMIT
https://github.com/honojs/hono/commit/48fa2233bc092f650119f42df043050737cabf39
Hono Source Repository REPOSITORY
https://github.com/honojs/hono
Hono Release RELEASE
https://github.com/honojs/hono/releases/tag/v4.12.12

Frequently Asked Questions

What is CVE-2026-39409?
CVE-2026-39409 is a security vulnerability in Hono involving Hono has incorrect IP matching in ipRestriction() for IPv4-mapped IPv6 addresses under CWE-180: Incorrect Behavior Order: Validate Before Canonicalize.
Which Hono versions are affected?
Affected versions include releases prior to 4.12.12 across affected packages: hono.
What version fixes CVE-2026-39409?
Upgrading to 4.12.12 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hono affected?
Yes, hono is affected in releases prior to 4.12.12. Upgrade your dependency to 4.12.12 or later.
What is the CVSS score of CVE-2026-39409?
CVE-2026-39409 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:L/I:N/A:N.
What CWE is associated with CVE-2026-39409?
CVE-2026-39409 is classified under CWE-180: Incorrect Behavior Order: Validate Before Canonicalize (The product validates input before it is canonicalized, which prevents the product from detecting data that becomes invalid after the canonicalization step.).
How can I check npm dependencies for CVE-2026-39409?
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-xpcf-pg52-r92g",
  "modified" : "2026-04-24T21:06:13Z",
  "published" : "2026-04-08T00:17:14Z",
  "aliases" : [ "CVE-2026-39409" ],
  "summary" : "Hono has incorrect IP matching in ipRestriction() for IPv4-mapped IPv6 addresses",
  "details" : "## Summary\n\n`ipRestriction()` does not canonicalize IPv4-mapped IPv6 client addresses (e.g. `::ffff:127.0.0.1`) before applying IPv4 allow or deny rules. In environments such as Node.js dual-stack, this can cause IPv4 rules to fail to match, leading to unintended authorization behavior.\n\n## Details\n\nThe middleware classifies client addresses based on their textual form. Addresses containing \"`:`\" are treated as IPv6, including IPv4-mapped IPv6 addresses such as `::ffff:127.0.0.1`. These addresses are not normalized to IPv4 before matching.\n\nAs a result:\n\n* IPv4 static rules (e.g. `127.0.0.1`) do not match because the raw string differs\n* IPv4 CIDR rules (e.g. `127.0.0.0/8`, `10.0.0.0/8`) are skipped because the address is treated as IPv6\n\nFor example, with:\n\n`denyList: ['127.0.0.1']`\n\na request from `127.0.0.1` may be represented as `::ffff:127.0.0.1` and bypass the deny rule.\n\nThis behavior commonly occurs in Node.js environments where IPv4 clients are exposed as IPv4-mapped IPv6 addresses.\n\n## Impact\n\nApplications that rely on IPv4-based `ipRestriction()` rules may incorrectly allow or deny requests.\n\nIn affected deployments, a denied IPv4 client may bypass access restrictions. Conversely, legitimate clients may be rejected when using IPv4 allow lists.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.12.12"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/security/advisories/GHSA-xpcf-pg52-r92g"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39409"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/commit/48fa2233bc092f650119f42df043050737cabf39"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/honojs/hono"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/releases/tag/v4.12.12"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-180" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-08T00:17:14Z",
    "nvd_published_at" : "2026-04-08T15:16:14Z"
  }
}