Hono Web Framework IP Address Validation Bypass Vulnerability in IP Restriction Middleware

A vulnerability allowing IP address validation bypass has been identified in the Hono web application framework, prior to version 4.11.7. The issue arises in the IP Restriction Middleware, where the IPV4_REGEX pattern and the convertIPv4ToBinary function in the ipaddr utility file fail to properly validate IPv4 octet values, allowing malformed IP addresses to bypass IP-based access controls. This vulnerability can be exploited by crafting specific IP addresses that manipulate the validation process, particularly when the application relies on client-provided IP information for access control decisions.

Impact

Exploitation of this vulnerability allows attackers to bypass IP-based access restrictions, potentially leading to unauthorized access or actions within the application. This includes circumventing blocklists and improperly exploiting allowlists by using crafted IP addresses that manipulate the application's IP validation logic.

Reproduction

The vulnerability can be reproduced by using an invalid IPv4 address that includes octet values greater than 255. This can be done by sending a request with the X-Forwarded-For header containing the malformed IP address. The Hono application will accept the address and convert it to binary, bypassing any IP restrictions that rely on correct octet validation.

Remediation

Users are advised to upgrade to Hono version 4.11.7 or later, where this vulnerability has been patched.