CVE-2026-24398
ADVISORY - githubSummary
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:
- 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). - Unsafe binary conversion: The
convertIPv4ToBinaryfunction 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
1.2.3.0/24is blocked, an attacker can use1.2.2.355(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
GitHub
2.2
CVSS SCORE
4.8medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| hono | npm | - | - | <4.11.7 | 4.11.7 |
CVSS:3 Severity and metrics
The CVSS metrics represent different qualitative aspects of a vulnerability that impact the overall score, as defined by the CVSS Specification.
The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone). One example of an Adjacent attack would be an ARP (IPv4) or neighbor discovery (IPv6) flood leading to a denial of service on the local LAN segment (e.g., CVE-2013-6014).
A successful attack depends on conditions beyond the attacker's control, requiring investing a measurable amount of effort in research, preparation, or execution against the vulnerable component before a successful attack.
The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
The vulnerable system can be exploited without interaction from any user.
An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
There is no impact to availability within the impacted component.
NIST
2.2