CVE-2026-111757: honojs hono Double Decoding of the Same Data

Vulnerability summary

CVE-2026-111757 is a medium (CVSS 5.3) Double Decoding of the Same Data vulnerability in honojs hono. EPSS estimates a 0.22% chance of exploitation in the next 30 days, higher than 12% of scored vulnerabilities.

Timeline

1. 19-10-2026
   PublishedVulnerability first disclosed.

Description

Hono is a Web application framework that provides support for any JavaScript runtime. From 4.12.4 until 4.13.11, serveStatic can interpret a malformed percent-encoded path differently from upstream routing middleware and bypass protection for a static prefix. The root cause is serveStatic decodes a routed request path a second time before filesystem lookup. The attack mechanism is malformed percent encoding survives the first routing interpretation and becomes a protected path only during the later static-file decode. The affected component is serveStatic. The trigger conditions are an application protects a static prefix with upstream middleware and serveStatic receives an attacker-controlled malformed percent-encoded path. The impact is unauthorized disclosure of a static file that upstream middleware was intended to protect. The issue does not permit traversal outside the configured static root. This issue is fixed in version 4.13.11.

• CWE-174Double Decoding of the Same DataThe product decodes the same input twice, which can limit the effectiveness of any protection mechanism that occurs in between the decoding operations.