CVE-2026-47674
ADVISORY - githubSummary
Summary
The ip-restriction middleware (hono/ip-restriction) compares incoming IP addresses against configured deny and allow rules using string equality after partial normalization. Non-canonical IPv6 representations of an address already listed in a static rule — such as compressed forms, explicit-zero forms, or hex-notation IPv4-mapped addresses — do not match the normalized rule entry, causing the rule to be silently skipped.
Details
When the rule matcher is built, each configured IP rule is normalized to a canonical string form. Incoming IP addresses received at request time are then compared against those canonical strings without applying the same normalization. Because IPv6 permits multiple syntactically different representations of the same numeric address, a non-canonical form of a denied address fails the string lookup and proceeds to the CIDR check, which also finds no match for rules registered as static (no prefix length). The request is then allowed.
Affected non-canonical forms include:
- Compressed versus expanded notation (
2001:db8::1vs2001:db8:0:0:0:0:0:1) - Hex-notation IPv4-mapped addresses (
::ffff:7f00:1vs::ffff:127.0.0.1) - Zone identifier suffixes (e.g.,
fe80::1%eth0)
Additionally, invalid IP address strings provided as the remote address are not rejected and may result in unexpected allow or deny behavior.
This issue arises when applications use ipRestriction() with static (non-CIDR) rules and the IP address source can supply addresses in non-canonical IPv6 form.
Impact
A request from an IP address covered by a static deny rule may bypass the restriction if the address is presented in a non-canonical IPv6 form.
This may lead to:
- Unauthorized access to endpoints intended to be restricted to specific IP addresses
- Bypass of IP-based access controls in environments where the runtime or an upstream proxy provides source addresses in a form that differs from the canonical form used in the rule configuration
This issue affects applications using hono/ip-restriction with static deny rules for IPv4 or IPv6 addresses, particularly when the source address is derived from proxy headers or custom getIP implementations that may return non-canonical forms.
GitHub
CVSS SCORE
5.3medium| Package | Type | OS Name | OS Version | Affected Ranges | Fix Versions |
|---|---|---|---|---|---|
| hono | npm | - | - | <4.12.21 | 4.12.21 |
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).
Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success when attacking the vulnerable component.
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 no loss of confidentiality.
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.