CyberRota Analysis
AI-GeneratedThe vulnerability affects the Hono web application framework for Java, specifically in versions 4.12.12 to 4.13.5, where the toSSG() function can write files outside the designated output directory due to insufficient normalization of route parameters. This flaw can lead to unauthorized file creation or overwriting in the build environment, potentially compromising generated artifacts. Developers utilizing Hono for static site generation, especially those incorporating user-controlled input, should prioritize upgrading to version 4.13.5 to mitigate this risk.
Public Exploit Signal
A public exploit, PoC, GitHub repository or Metasploit reference was detected for this CVE.
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Original NVD Description
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.