CVE-2026-39407: Hono Middleware Bypass Vulnerability
MODERATECVE-2026-39407 is a MODERATE (CVSS 5.3) middleware bypass vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Hono libraries in the npm ecosystem. The issue involves middleware bypass via repeated slashes in servestatic. Remediation is available by upgrading affected packages to version 4.12.12.
CVE-2026-39407 at a Glance
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).
How to Fix CVE-2026-39407
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.
npm install hono@4.12.12Run the following command in your project directory to verify that all resolved dependencies use the patched release:
npm ls honoHow to Check if You Are Affected
To determine whether your Node.js application is affected by CVE-2026-39407, inspect your project dependencies using npm:
npm ls honoAnalyze 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
CVE-2026-39407 Affected Hono Versions
1 component(s)| Product / Package | Ecosystem | Affected Versions | Fixed Version |
|---|---|---|---|
|
hono
|
npm |
< 4.12.12
|
4.12.12
|
References
Frequently Asked Questions
What is CVE-2026-39407?
Which Hono versions are affected?
What version fixes CVE-2026-39407?
Is hono affected?
What is the CVSS score of CVE-2026-39407?
What CWE is associated with CVE-2026-39407?
How can I check npm dependencies for CVE-2026-39407?
Machine-readable OSV JSON
OSV v1.5 Schema
{
"schema_version" : "1.4.0",
"id" : "GHSA-wmmm-f939-6g9c",
"modified" : "2026-04-08T15:34:30Z",
"published" : "2026-04-08T00:16:45Z",
"aliases" : [ "CVE-2026-39407" ],
"summary" : "Hono: Middleware bypass via repeated slashes in serveStatic",
"details" : "## Summary\n\nA path handling inconsistency in `serveStatic` allows protected static files to be accessed by using repeated slashes (`//`) in the request path.\n\nWhen route-based middleware (e.g., `/admin/*`) is used for authorization, the router may not match paths containing repeated slashes, while serveStatic resolves them as normalized paths. This can lead to a middleware bypass.\n\n## Details\n\nThe routing layer and `serveStatic` handle repeated slashes differently.\n\nFor example:\n\n```\n/admin/secret.txt => matches /admin/*\n/admin//secret.txt => may not match /admin/*\n```\n\nHowever, `serveStatic` may interpret both paths as the same file location (e.g., `admin/secret.txt`) and return the file.\n\nThis inconsistency allows a request such as:\n\n```\nGET //admin/secret.txt\n```\n\nto bypass middleware registered on `/admin/*` and access protected files.\n\nThe issue has been fixed by rejecting paths that contain repeated slashes, ensuring consistent behavior between route matching and static file resolution.\n\n## Impact\n\nAn attacker can access static files that are intended to be protected by route-based middleware by using repeated slashes in the request path.\n\nThis can lead to unauthorized access to sensitive files under the static root.\n\nThis issue affects applications that rely on serveStatic together with route-based middleware for access control.",
"severity" : [ {
"type" : "CVSS_V3",
"score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A: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-wmmm-f939-6g9c"
}, {
"type" : "ADVISORY",
"url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-39407"
}, {
"type" : "WEB",
"url" : "https://github.com/honojs/hono/commit/9aff14bd727f8b0435c963363fd803260e7b8e3c"
}, {
"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" : "2026-04-08T00:16:45Z",
"nvd_published_at" : "2026-04-08T15:16:14Z"
}
}