GHSA-xrhx-7g5j-rcj5 CVE-2026-47674
Hono: IP Restriction bypasses static deny rules for non-canonical IPv6
- Severity
- 5.3 / 10
- Medium · CVSS 3.1
- Exploit chance (EPSS)
- 0.24%
- Chance of exploitation in the next 30 days. Higher than 15.66% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-1289 Improper Validation of Unsafe Equivalence in Input
- CWE-185 Incorrect Regular Expression
- Fix
4.12.21- Upgrade hono to this version or later
Description
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.
Affected versions
npm
| Package | Vulnerable | Fixed in |
|---|---|---|
| hono | < 4.12.21 |
4.12.21 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
hono npm → 4.12.21
- npm
npm install hono@4.12.21- yarn
yarn add hono@4.12.21- pnpm
pnpm add hono@4.12.21
Severity breakdown
CVSS 3.1 5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- Low
- Availability
- None
Weakness
CWE-1289: Improper Validation of Unsafe Equivalence in Input
The product receives an input value that is used as a resource identifier or other type of reference, but it does not validate or incorrectly validates that the input is equivalent to a potentially-unsafe value.
How to prevent it
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
CWE-185: Incorrect Regular Expression
The product specifies a regular expression in a way that causes data to be improperly matched or compared.
How to prevent it
- Implementation: Regular expressions can become error prone when defining a complex language even for those experienced in writing grammars. Determine if several smaller regular expressions simplify one large regular expression. Also, subject the regular expression to thorough testing techniques such as equivalence partitioning, boundary value analysis, and robustness. After testing and a reasonable confidence level is achieved, a regular expression may not be foolproof. If an exploit is allowed to slip through, then record the exploit and refactor the regular expression.
References
Advisories
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-5r4p-p66f-jhc7 Hono: `serveStatic` decodes the request path a second time, leading to bypass of middleware on static paths | Medium | Also affects hono |
| GHSA-hxh3-vqpv-xpqv hono/jsx renders plain strings unescaped in boundary components, leading to XSS | Low | Also affects hono |
| GHSA-gqvv-2mrq-wpjv Hono: Incomplete fix for CVE-2026-39408: `toSSG()` still writes files outside the output directory | Medium | Also affects hono |
| GHSA-g6gw-c38x-mqfc Hono: Unbounded dot-notation nesting in `parseBody()` can cause memory exhaustion | Medium | Also affects hono |
| GHSA-crvj-82cr-hjcx Hono: Query parser reads parameters after the URL fragment, causing cache-key and proxy interpretation differentials | Medium | Also affects hono |
| GHSA-f23p-vx2j-j53r Hono: `memo()` retains SSR output across requests, leading to cross-user data disclosure | Medium | Also affects hono |
| GHSA-79qm-7rj5-m7r9 Hono: Proxy Helper does not remove response headers listed in the `Connection` header | Low | Also affects hono |
| GHSA-54fx-42gc-7vw4 Hono: Algorithmic Complexity DoS in Language Middleware | Medium | Also affects hono |
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