CVE-2026-24398: Hono Package IP Address Validation Bypass Vulnerability

Background

Hono is an open-source framework designed for building cloud-native applications. It provides various middleware components, including IP Restriction Middleware, which is intended to enforce access control based on client IP addresses. However, a flaw in the IP address validation process exposes the application to potential IP spoofing attacks, undermining the security of the access control mechanisms.

Vulnerability Detail

The vulnerability in Hono's IP Restriction Middleware arises from an improper validation of IPv4 addresses. The regex pattern used for validation allows octet values to exceed the valid range of 0-255, enabling attackers to craft malformed IP addresses that can bypass IP-based access controls. Specifically, the IPV4_REGEX pattern accepts values like '999', and the convertIPv4ToBinary function does not check octet ranges before performing bitwise operations. This can lead to unauthorized access, as attackers can exploit this flaw to bypass blocklists and allowlists by using crafted IP addresses.

npm install hono@4.13.13

npm install hono@4.11.7

Workaround

As a temporary workaround, you can implement additional validation checks in your application to ensure that all octets of the IP address are within the range of 0-255 before processing them. For example, you can use the following code snippet to validate the IP address:

function isValidIPv4(ip) {
  const octets = ip.split('.');
  if (octets.length !== 4) return false;
  return octets.every(octet => {
    const num = parseInt(octet, 10);
    return num >= 0 && num <= 255;
  });
}

Conclusion

The IP address validation bypass vulnerability in Hono's IP Restriction Middleware poses a significant risk to applications relying on IP-based access controls. By updating to the patched version and implementing additional validation checks, developers can mitigate the risks associated with this vulnerability.

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