honojs Hono up to 4.13.4 Static Site Generation toSSG ssgParams path traversal

Summaryinfo

A vulnerability identified as problematic has been detected in honojs Hono up to 4.13.4. This vulnerability affects the function toSSG of the component Static Site Generation. Performing a manipulation of the argument ssgParams results in path traversal. This vulnerability is reported as CVE-2026-84365. The attack is possible to be carried out remotely. No exploit exists.

Detailsinfo

A vulnerability classified as problematic has been found in honojs Hono up to 4.13.4. This affects the function toSSG of the component Static Site Generation. The manipulation of the argument ssgParams with an unknown input leads to a path traversal vulnerability. CWE is classifying the issue as CWE-22. 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. This is going to have an impact on integrity. The summary by CVE is:

Hono is a Web application framework that provides support for any JavaScript runtime. From 4.12.12 until 4.13.5, the fix released for CVE-2026-39408 does not cover every traversal sequence, and toSSG() can still write files outside the configured output directory when a route parameter contains consecutive parent-directory segments. Static site generation builds each output path from the route path and values supplied through ssgParams, then verifies that the result stays inside the output directory using the same normalization routine that built the path. That routine does not fully collapse runs of consecutive parent-directory segments, allowing a path that the check accepts to resolve outside the output directory, and the check also treats output directories that differ in how they are rooted as equivalent. This arises when an application generates a static site from route parameter values it does not fully control, such as slugs from a CMS, API, or user submission. An untrusted ssgParams value can create or overwrite files elsewhere in the build environment and alter generated artifacts or deployment output. The vulnerability affects build-time static site generation only; request-time routing and applications with entirely developer-controlled ssgParams values are not affected. This issue is fixed in version 4.13.5.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-84365 since 09/01/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1006 for this issue.

Upgrading to version 4.13.5 eliminates this vulnerability.

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Productinfo

Vendor

• honojs

Name

• Hono

Version

• 4.13.0
• 4.13.1
• 4.13.2
• 4.13.3
• 4.13.4

Website

• Product: https://github.com/honojs/hono/

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