CVE-2026-39408: hono Path Traversal

Vulnerability summary

CVE-2026-39408 is a high (CVSS 7.5) Path Traversal vulnerability in hono. EPSS estimates a 0.45% chance of exploitation in the next 30 days, higher than 38% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 08-04-2026
   PublishedVulnerability first disclosed.
2. 10-04-2026
   Last modifiedVulnerability information updated.

Description

Hono is a Web application framework that provides support for any JavaScript runtime. Prior to 4.12.12, 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. This vulnerability is fixed in 4.12.12.

• CWE-22Improper 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.