Common Weakness Enumeration

CWE-1289

Allowed

Improper Validation of Unsafe Equivalence in Input

Abstraction: Base · Status: Incomplete

API response cwe.mitre.org

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.

52 vulnerabilities reference this CWE, most recent first.

GHSA-W2Q5-6Q6X-X959

Vulnerability from github – Published: 2026-05-26 13:30 – Updated: 2026-07-15 12:31
VLAI
Details

The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode("xn--example-.com") incorrectly returns the name "example.com" rather than an error. This behavior can lead to privilege escalation in programs using the idna package. For example, a program which performs privilege checks on the ASCII hostname may reject "example.com" but permit "xn--example-.com". If that program subsequently converts the ASCII hostname to Unicode, it will inadvertently permits access to the Unicode name "example.com".

Severity
10.0 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2026-39821"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1289"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-05-22T16:16:20Z",
    "severity": "CRITICAL"
  },
  "details": "The ToASCII and ToUnicode functions incorrectly accept Punycode-encoded labels that decode to an ASCII-only label. For example, ToUnicode(\"xn--example-.com\") incorrectly returns the name \"example.com\" rather than an error. This behavior can lead to privilege escalation in programs using the idna package. For example, a program which performs privilege checks on the ASCII hostname may reject \"example.com\" but permit \"xn--example-.com\". If that program subsequently converts the ASCII hostname to Unicode, it will inadvertently permits access to the Unicode name \"example.com\".",
  "id": "GHSA-w2q5-6q6x-x959",
  "modified": "2026-07-15T12:31:47Z",
  "published": "2026-05-26T13:30:18Z",
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  "severity": [
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      "type": "CVSS_V3"
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}

GHSA-XRHX-7G5J-RCJ5

Vulnerability from github – Published: 2026-06-04 18:00 – Updated: 2026-06-04 18:00
VLAI
Summary
Hono: IP Restriction bypasses static deny rules for non-canonical IPv6
Details

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::1 vs 2001:db8:0:0:0:0:0:1)
  • Hex-notation IPv4-mapped addresses (::ffff:7f00:1 vs ::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.

Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "hono"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.12.21"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-47674"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1289",
      "CWE-185"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-04T18:00:22Z",
    "nvd_published_at": "2026-05-28T17:16:32Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\nThe `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 \u2014 such as compressed forms, explicit-zero forms, or hex-notation IPv4-mapped addresses \u2014 do not match the normalized rule entry, causing the rule to be silently skipped.\n\n### Details\n\nWhen 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.\n\nAffected non-canonical forms include:\n\n- Compressed versus expanded notation (`2001:db8::1` vs `2001:db8:0:0:0:0:0:1`)\n- Hex-notation IPv4-mapped addresses (`::ffff:7f00:1` vs `::ffff:127.0.0.1`)\n- Zone identifier suffixes (e.g., `fe80::1%eth0`)\n\nAdditionally, invalid IP address strings provided as the remote address are not rejected and may result in unexpected allow or deny behavior.\n\nThis issue arises when applications use `ipRestriction()` with static (non-CIDR) rules and the IP address source can supply addresses in non-canonical IPv6 form.\n\n### Impact\n\nA 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.\n\nThis may lead to:\n\n- Unauthorized access to endpoints intended to be restricted to specific IP addresses\n- 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\n\nThis 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.",
  "id": "GHSA-xrhx-7g5j-rcj5",
  "modified": "2026-06-04T18:00:22Z",
  "published": "2026-06-04T18:00:22Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/honojs/hono/security/advisories/GHSA-xrhx-7g5j-rcj5"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-47674"
    },
    {
      "type": "WEB",
      "url": "https://github.com/honojs/hono/commit/c831020fb1fa2e929d222f6c84e1abfe013e512b"
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      "type": "PACKAGE",
      "url": "https://github.com/honojs/hono"
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      "type": "WEB",
      "url": "https://github.com/honojs/hono/releases/tag/v4.12.21"
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  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Hono: IP Restriction bypasses static deny rules for non-canonical IPv6 "
}
Mitigation MIT-5
Implementation

Strategy: Input Validation

  • 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.

No CAPEC attack patterns related to this CWE.

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