GHSA-V2V4-37R5-5V8G

Vulnerability from github – Published: 2026-05-05 21:50 – Updated: 2026-05-13 16:27
VLAI?
Summary
ip-address has XSS in Address6 HTML-emitting methods
Details

Summary

Address6.group() and Address6.link() do not HTML-escape attacker-controlled content before embedding it in the HTML strings they return, and AddressError.parseMessage (emitted by the Address6 constructor for invalid input) can contain unescaped attacker-controlled content in one branch. An application that (1) passes untrusted input to Address6 and (2) renders the output of these methods, or the thrown error's parseMessage, as HTML (e.g. via innerHTML) is vulnerable to cross-site scripting. A related issue in v6.helpers.spanAll() produced malformed markup but was not exploitable; it is hardened in the same release for consistency.

Details

Four related issues were identified and fixed together:

  1. Address6.group(): zone ID injection. The Address6 constructor stores the raw input (including any IPv6 zone ID) in this.address before zone stripping. group() then passed this.address to helpers.simpleGroup(), which wrapped each :-separated segment in a <span> element without HTML-escaping the content. A zone ID containing HTML markup was embedded verbatim.
  2. Address6.link({ prefix, className }): attribute-value injection. link() concatenated user-supplied prefix and className into the href="…" and class="…" attributes without escaping. A caller passing untrusted content through these options could inject event handlers (e.g. onmouseover) and achieve XSS.
  3. Address6 constructor: leading-zero IPv4 error path. The leading-zero branch in parse4in6() built AddressError.parseMessage by concatenating the raw address through String.replace(). Because parse4in6() runs before the bad-character check, any characters in the groups preceding the IPv4 suffix flowed into the error's HTML unescaped. Consumers who render parseMessage as HTML (its documented purpose — it already contains <span class="parse-error"> markup) could be XSS'd by a crafted input such as <img src=x onerror=alert(1)>:10.0.01.1.
  4. v6.helpers.spanAll(): attribute-value injection (defense in depth). spanAll() embedded each character of its input into a class="digit value-${n} …" attribute without escaping. Because split('') limits n to a single character this was not exploitable in practice, but it produced malformed markup and is fixed for consistency.

Affected Versions

All versions up to and including 10.1.0.

Patched Version

10.1.1.

Impact

Real-world exposure is believed to be extremely limited. Analysis of all 425 dependent npm packages as well as GitHub code search found zero consumers of group(), link(), or spanAll(): these HTML-emitting surfaces appear to be unused across published npm packages and public repositories. Applications using only the address-parsing and comparison APIs (isValid, correctForm, isInSubnet, bigInt, etc.) are not affected.

Consumers who do render the output of group(), link(), spanAll(), or AddressError.parseMessage as HTML against untrusted input should upgrade.

PoC

const { Address6 } = require('ip-address');
const addr = new Address6('fe80::1%<img src=x onerror=alert(1)>');
document.body.innerHTML = addr.group();  // fires the onerror handler in 10.1.0

Workarounds

If users cannot upgrade immediately:

  • Do not pass untrusted input to the Address6 constructor, or
  • Never render the output of group(), link(), or spanAll(), nor the parseMessage field of any thrown AddressError, as HTML; treat these values as text only, or run them through DOMPurify before inserting into the DOM (DOMPurify's default configuration preserves the library's intended <span> wrapping while stripping any injected event handlers), or
  • Validate input with Address6.isValid() and reject anything that contains a zone identifier (a % character) or characters outside [0-9a-fA-F:/] before passing it to the constructor.

Lack of separate CVEs

Given the evidence that these methods are not used, and given that they are all of the same construction, maintainers do not think it's relevant or useful to create a separate CVE for each library method.

Credit

ip-address thanks @scovetta for reporting this issue.

Severity ?
5.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 10.1.0"
      },
      "package": {
        "ecosystem": "npm",
        "name": "ip-address"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "10.1.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-42338"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-05T21:50:58Z",
    "nvd_published_at": "2026-05-12T20:16:41Z",
    "severity": "MODERATE"
  },
  "details": "### Summary\n\n`Address6.group()` and `Address6.link()` do not HTML-escape attacker-controlled content before embedding it in the HTML strings they return, and `AddressError.parseMessage` (emitted by the `Address6` constructor for invalid input) can contain unescaped attacker-controlled content in one branch. An application that (1) passes untrusted input to `Address6` and (2) renders the output of these methods, or the thrown error\u0027s `parseMessage`, as HTML (e.g. via `innerHTML`) is vulnerable to cross-site scripting. A related issue in `v6.helpers.spanAll()` produced malformed markup but was not exploitable; it is hardened in the same release for consistency.\n\n### Details\n\nFour related issues were identified and fixed together:\n\n1. **`Address6.group()`: zone ID injection.** The `Address6` constructor stores the raw input (including any IPv6 zone ID) in `this.address` before zone stripping. `group()` then passed `this.address` to `helpers.simpleGroup()`, which wrapped each `:`-separated segment in a `\u003cspan\u003e` element without HTML-escaping the content. A zone ID containing HTML markup was embedded verbatim.\n2. **`Address6.link({ prefix, className })`: attribute-value injection.** `link()` concatenated user-supplied `prefix` and `className` into the `href=\"\u2026\"` and `class=\"\u2026\"` attributes without escaping. A caller passing untrusted content through these options could inject event handlers (e.g. `onmouseover`) and achieve XSS.\n3. **`Address6` constructor: leading-zero IPv4 error path.** The leading-zero branch in `parse4in6()` built `AddressError.parseMessage` by concatenating the raw address through `String.replace()`. Because `parse4in6()` runs before the bad-character check, any characters in the groups preceding the IPv4 suffix flowed into the error\u0027s HTML unescaped. Consumers who render `parseMessage` as HTML (its documented purpose \u2014 it already contains `\u003cspan class=\"parse-error\"\u003e` markup) could be XSS\u0027d by a crafted input such as `\u003cimg src=x onerror=alert(1)\u003e:10.0.01.1`.\n4. **`v6.helpers.spanAll()`: attribute-value injection (defense in depth).** `spanAll()` embedded each character of its input into a `class=\"digit value-${n} \u2026\"` attribute without escaping. Because `split(\u0027\u0027)` limits `n` to a single character this was not exploitable in practice, but it produced malformed markup and is fixed for consistency.\n\n### Affected Versions\n\nAll versions up to and including `10.1.0`.\n\n### Patched Version\n\n`10.1.1`.\n\n### Impact\n\nReal-world exposure is believed to be extremely limited. Analysis of all 425 dependent npm packages as well as GitHub code search found zero consumers of `group()`, `link()`, or `spanAll()`: these HTML-emitting surfaces appear to be unused across published npm packages and public repositories. Applications using only the address-parsing and comparison APIs (`isValid`, `correctForm`, `isInSubnet`, `bigInt`, etc.) are not affected.\n\nConsumers who **do** render the output of `group()`, `link()`, `spanAll()`, or `AddressError.parseMessage` as HTML against untrusted input should upgrade.\n\n### PoC\n\n```javascript\nconst { Address6 } = require(\u0027ip-address\u0027);\nconst addr = new Address6(\u0027fe80::1%\u003cimg src=x onerror=alert(1)\u003e\u0027);\ndocument.body.innerHTML = addr.group();  // fires the onerror handler in 10.1.0\n```\n\n### Workarounds\n\nIf users cannot upgrade immediately:\n\n- Do not pass untrusted input to the `Address6` constructor, or\n- Never render the output of `group()`, `link()`, or `spanAll()`, nor the `parseMessage` field of any thrown `AddressError`, as HTML; treat these values as text only, or run them through [DOMPurify](https://github.com/cure53/DOMPurify) before inserting into the DOM (DOMPurify\u0027s default configuration preserves the library\u0027s intended `\u003cspan\u003e` wrapping while stripping any injected event handlers), or\n- Validate input with `Address6.isValid()` and reject anything that contains a zone identifier (a `%` character) or characters outside `[0-9a-fA-F:/]` before passing it to the constructor.\n\n### Lack of separate CVEs\n\nGiven the evidence that these methods are not used, and given that they are all of the same construction, maintainers do not think it\u0027s relevant or useful to create a separate CVE for each library method.\n\n### Credit\n\nip-address thanks @scovetta for reporting this issue.",
  "id": "GHSA-v2v4-37r5-5v8g",
  "modified": "2026-05-13T16:27:24Z",
  "published": "2026-05-05T21:50:58Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/beaugunderson/ip-address/security/advisories/GHSA-v2v4-37r5-5v8g"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-42338"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/beaugunderson/ip-address"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "ip-address has XSS in Address6 HTML-emitting methods"
}


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