CVE-2026-39408: Hono Path Traversal Vulnerability

MODERATE
Advisory Identifier: GHSA-xf4j-xp2r-rqqx
Share
CWE-22
Published
Advisory Summary

CVE-2026-39408 is a MODERATE path traversal vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Hono libraries in the npm ecosystem. The issue involves path traversal in tossg() allows writing files outside the output directory. Remediation is available by upgrading affected packages to version 4.12.12.

CVE-2026-39408 at a Glance

CVE Identifier CVE-2026-39408
GHSA Identifier GHSA-xf4j-xp2r-rqqx
Severity MODERATE
CVSS v3.1 Base Score N/A
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Hono
Package Ecosystem npm
Published Date
Last Updated

How to Fix CVE-2026-39408

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-2026-39408, 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-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. 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 A path traversal issue in `toSSG()` allows files to be written outside the configured output directory during static site generation. When using dynamic route parameters via `ssgParams`, specially crafted values can cause generated file paths to escape the intended output directory. ## Details The static site generation process creates output files based on route paths derived from application routes and parameters. When `ssgParams` is used to provide values for dynamic routes, those values are used to construct output file paths. If these values contain traversal sequences (e.g. `..`), the resulting output path may resolve outside the configured output directory. As a result, files may be written to unintended locations instead of being confined within the specified output directory. For example: ```ts import { Hono } from 'hono' import { toSSG, ssgParams } from 'hono/ssg' const app = new Hono() app.get('/:id', ssgParams([{ id: '../pwned' }]), (c) => { return c.text('pwned') }) toSSG(app, fs, { dir: './static' }) ``` In this case, the generated output path may resolve outside `./static`, resulting in a file being written outside the intended output directory. ## Impact An attacker who can influence values passed to `ssgParams` during the build process may be able to write files outside the intended output directory. Depending on the build and deployment environment, this may: * overwrite unintended files * affect generated artifacts * impact deployment outputs or downstream tooling This issue is limited to build-time static site generation and does not affect request-time routing.

CVE-2026-39408 Affected Hono Versions

1 component(s)
Fixed Versions:
4.12.12
Product / Package Ecosystem Affected Versions Fixed Version
hono
npm/hono
npm
≥ 4.0.0
< 4.12.12
4.12.12

References

GitHub Advisory / Wiki ADVISORY
https://github.com/honojs/hono/security/advisories/GHSA-xf4j-xp2r-rqqx
NVD — CVE-2026-39408 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39408
Security Fix Commit FIX COMMIT
https://github.com/honojs/hono/commit/b470278920fffcfd6d76002755d6db53db827679
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-2026-39408?
CVE-2026-39408 is a security vulnerability in Hono involving Path traversal in toSSG() allows writing files outside the output directory under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Hono versions are affected?
Affected versions include releases prior to 4.12.12 across affected packages: hono.
What version fixes CVE-2026-39408?
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 CWE is associated with CVE-2026-39408?
CVE-2026-39408 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check npm dependencies for CVE-2026-39408?
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-xf4j-xp2r-rqqx",
  "modified" : "2026-04-08T15:34:35Z",
  "published" : "2026-04-08T00:16:51Z",
  "aliases" : [ "CVE-2026-39408" ],
  "summary" : "Hono: Path traversal in toSSG() allows writing files outside the output directory",
  "details" : "## Summary\n\nA path traversal issue in `toSSG()` allows files to be written outside the configured output directory during static site generation. When using dynamic route parameters via `ssgParams`, specially crafted values can cause generated file paths to escape the intended output directory.\n\n## Details\n\nThe static site generation process creates output files based on route paths derived from application routes and parameters. When `ssgParams` is used to provide values for dynamic routes, those values are used to construct output file paths. If these values contain traversal sequences (e.g. `..`), the resulting output path may resolve outside the configured output directory. As a result, files may be written to unintended locations instead of being confined within the specified output directory.\n\nFor example:\n \n```ts\nimport { Hono } from 'hono'\nimport { toSSG, ssgParams } from 'hono/ssg'\n\nconst app = new Hono()\n\napp.get('/:id', ssgParams([{ id: '../pwned' }]), (c) => {\n  return c.text('pwned')\n})\n\ntoSSG(app, fs, { dir: './static' })\n```\n\nIn this case, the generated output path may resolve outside `./static`, resulting in a file being written outside the intended output directory.\n\n## Impact\n\nAn attacker who can influence values passed to `ssgParams` during the build process may be able to write files outside the intended output directory.\n\nDepending on the build and deployment environment, this may:\n\n* overwrite unintended files\n* affect generated artifacts\n* impact deployment outputs or downstream tooling\n\nThis issue is limited to build-time static site generation and does not affect request-time routing.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:L/AC:H/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.12.12"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.12.11"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/security/advisories/GHSA-xf4j-xp2r-rqqx"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39408"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/commit/b470278920fffcfd6d76002755d6db53db827679"
  }, {
    "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-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-08T00:16:51Z",
    "nvd_published_at" : "2026-04-08T15:16:14Z"
  }
}