CVE-2026-118663 in node-server
Summary
by MITRE • 10/28/2026
@hono/node-server allows running the Hono application on Node.js. From 1.19.10 until 2.1.3, serveStatic decodes a request path a second time after Hono has already decoded it for routing, so a malformed percent-encoded sequence can make route middleware evaluate an encoded path while static file resolution uses a different directory. An unauthenticated attacker can bypass middleware mounted on a protected static prefix and read a file inside the configured static root, although the flaw does not permit traversal outside that root. This issue is fixed in version 2.1.3.
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Analysis
by VulDB Data Team • 10/28/2026
The vulnerability identified in @hono/node-server versions ranging from 1.19.10 to 2.1.3 represents a critical logic error within the static file serving mechanism, specifically affecting the serveStatic function. This component is responsible for handling requests intended to retrieve static assets such as images, stylesheets, and scripts. The core technical flaw stems from an inconsistency in how request paths are processed during different stages of the HTTP request lifecycle. When a client submits a request containing percent-encoded characters within the URL path, Hono initially decodes this path to facilitate route matching and middleware evaluation. However, subsequent processing by the serveStatic module performs a second decoding operation on what it perceives as an unencoded or differently encoded string. This double-decoding behavior creates a divergence between the logical view of the request used for security checks and routing decisions versus the physical file system access performed to locate the requested resource.
This discrepancy allows for a path traversal attack that bypasses middleware protections, particularly those mounted on protected static prefixes. In typical web application architectures, developers often mount specific middleware functions to enforce authentication or authorization requirements before allowing access to sensitive directories within the static root. Because the route middleware operates on the first decoded version of the URL while the file resolution system uses a second decoding that may interpret escape sequences differently, an attacker can craft a malformed percent-encoded sequence. This crafted payload causes the routing layer to believe the request is targeting a protected area or a specific safe endpoint, thereby allowing it to pass through authentication checks. Simultaneously, the static file resolver interprets the double-decoded path as pointing to a different location within the same directory tree. Consequently, an unauthenticated attacker can read files that should have been restricted by middleware logic.
The operational impact of this vulnerability is significant for applications relying on @hono/node-server for serving content with strict access controls. While the flaw does not permit traversal outside the configured static root directory, it effectively neutralizes security measures designed to restrict access to specific subdirectories or files within that root. Attackers can exploit this to expose sensitive configuration files, internal documentation, backup data, or other resources intended to be private. This undermines the principle of least privilege and compromises the confidentiality of application assets. The vulnerability is classified under CWE-20 Improper Input Validation because it involves a failure to correctly validate and normalize input paths before file system access. Furthermore, this technique aligns with ATT&CK tactic TA0001 Initial Access and specifically relates to techniques involving path traversal or directory indexing if the server allows listing, though in this case, it is primarily an unauthorized read of specific files due to logic flaws rather than generic enumeration.
To mitigate this vulnerability, organizations must immediately upgrade @hono/node-server to version 2.1.3 or later, where the double-decoding issue has been resolved and path normalization is handled consistently across routing and file serving modules. For environments that cannot update immediately, a temporary workaround involves implementing custom middleware that manually normalizes URL paths using standard decoding libraries before they reach any route handlers or static file servers. This ensures that all components of the application process the same canonical representation of the request URI. Additionally, developers should audit their use of serveStatic to ensure no reliance on implicit path handling behaviors and consider employing strict allowlists for permitted file extensions and directory structures where possible. Regular security testing using automated scanners capable of detecting double-encoding bypasses can help identify similar logic flaws in other parts of the application stack.