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GHSA-r354-f388-2fhh

MediumCVSS 4.8 / 10
Published Jan 27, 2026·Last modified Feb 12, 2026
Affected Components(0)

No affected components available

Description

Summary

IP Restriction Middleware in Hono is vulnerable to an IP address validation bypass. The IPV4_REGEX pattern and convertIPv4ToBinary function in src/utils/ipaddr.ts do not properly validate that IPv4 octet values are within the valid range of 0-255, allowing attackers to craft malformed IP addresses that bypass IP-based access controls.

Details

The vulnerability exists in two components:

  1. Permissive regex pattern: The IPV4_REGEX (/^[0-9]{0,3}\.[0-9]{0,3}\.[0-9]{0,3}\.[0-9]{0,3}$/) accepts octet values greater than 255 (e.g., 999).
  2. Unsafe binary conversion: The convertIPv4ToBinary function does not validate octet ranges before performing bitwise operations. When an octet exceeds 255, it overflows into adjacent octets during the bit-shift calculation.

For example, the IP address 1.2.2.355 is accepted and converts to the same binary value as 1.2.3.99:

  • 355 = 256 + 99 = 0x163
  • After bit-shifting: (1 << 24) + (2 << 16) + (2 << 8) + 355 = 0x01020363 = 1.2.3.99

Impact

An attacker can bypass IP-based restrictions by crafting malformed IP addresses:

  • Blocklist bypass: If 1.2.3.0/24 is blocked, an attacker can use 1.2.2.355 (or similar) to bypass the restriction.
  • Allowlist bypass: Requests from unauthorized IP ranges may be incorrectly permitted.

This is exploitable when the application relies on client-provided IP addresses (e.g., X-Forwarded-For header) for access control decisions.

Affected Components

  • IP Restriction Middleware
  • src/utils/ipaddr.ts: IPV4_REGEX, convertIPv4ToBinary, distinctRemoteAddr
Risk Scores
Base Score
4.8

The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a low impact on the confidentiality of the information. There is a low impact on the integrity of the data.

Threat Intelligence
4.4

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
0.32%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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Medium severity
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