Vulnerability-Lookup

GHSA-2V35-W6HQ-6MFW

Vulnerability from github – Published: 2026-04-22 20:23 – Updated: 2026-04-22 20:23

Summary

xmldom: Uncontrolled recursion in XML serialization leads to DoS

Details

Summary

Seven recursive traversals in lib/dom.js operate without a depth limit. A sufficiently deeply nested DOM tree causes a RangeError: Maximum call stack size exceeded, crashing the application.

Reported operations: - Node.prototype.normalize() — reported by @praveen-kv (email 2026-04-05) and @KarimTantawey (GHSA-fwmp-8wwc-qhv6, via DOMParser.parseFromString()) - XMLSerializer.serializeToString() — reported by @Jvr2022 (GHSA-2v35-w6hq-6mfw) and @KarimTantawey (GHSA-j2hf-fqwf-rrjf)

Additionally, discovered in research: - Element.getElementsByTagName() / getElementsByTagNameNS() / getElementsByClassName() / getElementById() - Node.cloneNode(true) - Document.importNode(node, true) - node.textContent (getter) - Node.isEqualNode(other)

All seven share the same root cause: pure-JavaScript recursive tree traversal with no depth guard. A single deeply nested document (parsed successfully) triggers any or all of these operations.

Details

Root cause

lib/dom.js implements DOM tree traversals as depth-first recursive functions. Each level of element nesting adds one JavaScript call frame. The JS engine's call stack is finite; once exhausted, a RangeError: Maximum call stack size exceeded is thrown. This error may not be caught reliably at stack-exhaustion depths because the catch handler itself requires stack frames to execute — especially in async scenarios, where an uncaught RangeError inside a callback or promise chain can crash the entire Node.js process.

Parsing a deeply nested document succeeds — the SAX parser in lib/sax.js is iterative. The crash occurs during subsequent operations on the parsed DOM.

`Node.prototype.normalize()` — reported by @praveen-kv

lib/dom.js:1296–1308 (main):

normalize: function () {
    var child = this.firstChild;
    while (child) {
        var next = child.nextSibling;
        if (next && next.nodeType == TEXT_NODE && child.nodeType == TEXT_NODE) {
            this.removeChild(next);
            child.appendData(next.data);
        } else {
            child.normalize();   // recursive call — no depth guard
            child = next;
        }
    }
},

Crash threshold (Node.js 18, default stack): ~10,000 levels.

`XMLSerializer.serializeToString()` — reported by @Jvr2022

lib/dom.js:2790–2974 (main): The internal serializeToString worker recurses into child nodes at four call sites, each passing a visibleNamespaces.slice() copy. The per-frame allocation causes earlier stack exhaustion than normalize().

Crash threshold (Node.js 18, default stack): ~5,000 levels.

Additional recursive entry points

All five crash at ~10,000 levels on Node.js 18.

Function	Definition	Public API entry point(s)	Crash depth (Node.js 18)
`_visitNode`	`lib/dom.js:1529`	`getElementsByTagName()`, `getElementsByTagNameNS()`, `getElementsByClassName()`, `getElementById()`	~10,000 levels
`cloneNode` (module fn)	`lib/dom.js:3037`	`Node.prototype.cloneNode(true)`	~10,000 levels
`importNode` (module fn)	`lib/dom.js:2975`	`Document.prototype.importNode(node, true)`	~10,000 levels
`getTextContent` (inner fn)	`lib/dom.js:3130`	`node.textContent` (getter)	~10,000 levels
`isEqualNode`	`lib/dom.js:1120`	`Node.prototype.isEqualNode(other)`	~10,000 levels

Both active branches (main and release-0.8.x) are identically affected. The unscoped xmldom package (≤ 0.6.0) carries the same recursive patterns from its initial commit.

Browser behavior

Tested with Chromium 147 (Playwright headless). Chromium's native C++ implementations of all seven DOM methods are iterative — they traverse the DOM without consuming JS call stack frames. All seven succeed at depths up to 20,000 without any crash.

When @xmldom/xmldom is bundled and run in a browser context the same recursive JS code executes under the browser's V8 stack limit (~12,000–13,000 frames). The crash thresholds are similar to those observed on Node.js 18 (~5,000 for serializeToString, ~10,000 for the remaining six).

The vulnerability is specific to xmldom's pure-JavaScript recursive implementation, not an inherent property of the DOM operations.

PoC

`normalize()` (from @praveen-kv report, 2026-04-05)

const { DOMParser } = require('@xmldom/xmldom');

function generateNestedXML(depth) {
    return '<root>' + '<a>'.repeat(depth) + 'text' + '</a>'.repeat(depth) + '</root>';
}

const doc = new DOMParser().parseFromString(generateNestedXML(10000), 'text/xml');
doc.documentElement.normalize();
// RangeError: Maximum call stack size exceeded

`XMLSerializer.serializeToString()` (from GHSA-2v35-w6hq-6mfw)

const { DOMParser, XMLSerializer } = require('@xmldom/xmldom');

const depth = 5000;
const xml = '<a>'.repeat(depth) + '</a>'.repeat(depth);
const doc = new DOMParser().parseFromString(xml, 'text/xml');
new XMLSerializer().serializeToString(doc);
// RangeError: Maximum call stack size exceeded

The other methods have been verified using similar pocs.

Impact

Any service that accepts attacker-controlled XML and subsequently calls any of the seven affected DOM operations can be forced into a reliable denial of service with a single crafted payload.

The immediate result is an uncaught RangeError and failed request processing. In deployments where uncaught exceptions terminate the worker or process, the impact can extend beyond a single request and disrupt service availability more broadly.

No authentication, special options, or invalid XML is required. A valid, deeply nested XML document is enough.

Disclosure

The normalize() vector was publicly disclosed at 2026-04-06T11:25:07Z via xmldom/xmldom#987 (closed without merge). serializeToString() and the five additional recursive entry points were not mentioned in that PR.

Fix Applied

All seven affected traversals have been converted from recursive to iterative implementations, eliminating call-stack consumption on deep trees.

`walkDOM` utility

A new walkDOM(node, context, callbacks) utility is introduced. It traverses the subtree rooted at node in depth-first order using an explicit JavaScript array as a stack, consuming heap memory instead of call-stack frames. context is an arbitrary value threaded through the walk — each callbacks.enter(node, context) call returns the context to pass to that node's children, enabling per-branch state (e.g. namespace snapshots in the serializer). callbacks.exit(node, context) (optional) is called in post-order after all children have been visited.

The following six operations are re-implemented on top of walkDOM:

Operation	Public entry point(s)
`_visitNode` helper	`getElementsByTagName()`, `getElementsByTagNameNS()`, `getElementsByClassName()`, `getElementById()`
`getTextContent` inner function	`node.textContent` getter
`cloneNode` module function	`Node.prototype.cloneNode(true)`
`importNode` module function	`Document.prototype.importNode(node, true)`
`serializeToString` worker	`XMLSerializer.prototype.serializeToString()`, `Node.prototype.toString()`, `NodeList.prototype.toString()`
`normalize`	`Node.prototype.normalize()`

normalize uses walkDOM with a null context and an enter callback that merges adjacent Text children of the current node before walkDOM reads and queues those children — so the surviving post-merge children are what the walker descends into.

Custom iterative loop for `isEqualNode`

One function cannot use walkDOM:

Node.prototype.isEqualNode(other) (0.9.x only; absent from 0.8.x) compares two trees in parallel. It maintains an explicit stack of {node, other} node pairs — one node from each tree — which cannot be expressed with walkDOM's single-tree visitor.

After the fix

All seven entry points succeed on trees of arbitrary depth without throwing RangeError. The original PoCs still demonstrate the vulnerability on unpatched versions and confirm the fix on patched versions.

Severity ?

8.7 (High)


                  
                    CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "@xmldom/xmldom"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.8.13"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "@xmldom/xmldom"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0.9.0"
            },
            {
              "fixed": "0.9.10"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "xmldom"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "0.6.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41673"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-674"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-22T20:23:57Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n\nSeven recursive traversals in `lib/dom.js` operate without a depth limit. A sufficiently deeply\nnested DOM tree causes a `RangeError: Maximum call stack size exceeded`, crashing the application.\n\n**Reported operations:**\n- `Node.prototype.normalize()` \u2014 reported by @praveen-kv (email 2026-04-05) and @KarimTantawey (GHSA-fwmp-8wwc-qhv6, via `DOMParser.parseFromString()`)\n- `XMLSerializer.serializeToString()` \u2014 reported by @Jvr2022 (GHSA-2v35-w6hq-6mfw) and @KarimTantawey (GHSA-j2hf-fqwf-rrjf)\n\n**Additionally, discovered in research:**\n- `Element.getElementsByTagName()` / `getElementsByTagNameNS()` / `getElementsByClassName()` / `getElementById()`\n- `Node.cloneNode(true)`\n- `Document.importNode(node, true)`\n- `node.textContent` (getter)\n- `Node.isEqualNode(other)`\n\nAll seven share the same root cause: pure-JavaScript recursive tree traversal with no depth guard.\nA single deeply nested document (parsed successfully) triggers any or all of these operations.\n\n---\n\n## Details\n\n### Root cause\n\n`lib/dom.js` implements DOM tree traversals as depth-first recursive functions. Each level of\nelement nesting adds one JavaScript call frame. The JS engine\u0027s call stack is finite; once\nexhausted, a `RangeError: Maximum call stack size exceeded` is thrown. This error may not be\ncaught reliably at stack-exhaustion depths because the catch handler itself requires stack\nframes to execute \u2014 especially in async scenarios, where an uncaught `RangeError` inside a\ncallback or promise chain can crash the entire Node.js process.\n\nParsing a deeply nested document **succeeds** \u2014 the SAX parser in `lib/sax.js` is iterative.\nThe crash occurs during subsequent operations on the parsed DOM.\n\n### `Node.prototype.normalize()` \u2014 reported by @praveen-kv\n\n[`lib/dom.js:1296\u20131308`](https://github.com/xmldom/xmldom/blob/9ef2fd297ca527a05ecb11979850317a927cd20c/lib/dom.js#L1296-L1308) (main):\n\n```js\nnormalize: function () {\n    var child = this.firstChild;\n    while (child) {\n        var next = child.nextSibling;\n        if (next \u0026\u0026 next.nodeType == TEXT_NODE \u0026\u0026 child.nodeType == TEXT_NODE) {\n            this.removeChild(next);\n            child.appendData(next.data);\n        } else {\n            child.normalize();   // recursive call \u2014 no depth guard\n            child = next;\n        }\n    }\n},\n```\n\nCrash threshold (Node.js 18, default stack): ~10,000 levels.\n\n### `XMLSerializer.serializeToString()` \u2014 reported by @Jvr2022\n\n[`lib/dom.js:2790\u20132974`](https://github.com/xmldom/xmldom/blob/9ef2fd297ca527a05ecb11979850317a927cd20c/lib/dom.js#L2790-L2974) (main):\nThe internal `serializeToString` worker recurses into child nodes at four call sites, each\npassing a `visibleNamespaces.slice()` copy. The per-frame allocation causes earlier stack\nexhaustion than `normalize()`.\n\nCrash threshold (Node.js 18, default stack): ~5,000 levels.\n\n### Additional recursive entry points\n\nAll five crash at ~10,000 levels on Node.js 18.\n\n| Function                    | Definition                                                                                                           | Public API entry point(s)                                                                            | Crash depth (Node.js 18) |\n|-----------------------------|----------------------------------------------------------------------------------------------------------------------|------------------------------------------------------------------------------------------------------|--------------------------|\n| `_visitNode`                | [`lib/dom.js:1529`](https://github.com/xmldom/xmldom/blob/9ef2fd297ca527a05ecb11979850317a927cd20c/lib/dom.js#L1529) | `getElementsByTagName()`, `getElementsByTagNameNS()`, `getElementsByClassName()`, `getElementById()` | ~10,000 levels           |\n| `cloneNode` (module fn)     | [`lib/dom.js:3037`](https://github.com/xmldom/xmldom/blob/9ef2fd297ca527a05ecb11979850317a927cd20c/lib/dom.js#L3037) | `Node.prototype.cloneNode(true)`                                                                     | ~10,000 levels           |\n| `importNode` (module fn)    | [`lib/dom.js:2975`](https://github.com/xmldom/xmldom/blob/9ef2fd297ca527a05ecb11979850317a927cd20c/lib/dom.js#L2975) | `Document.prototype.importNode(node, true)`                                                          | ~10,000 levels           |\n| `getTextContent` (inner fn) | [`lib/dom.js:3130`](https://github.com/xmldom/xmldom/blob/9ef2fd297ca527a05ecb11979850317a927cd20c/lib/dom.js#L3130) | `node.textContent` (getter)                                                                          | ~10,000 levels           |\n| `isEqualNode`               | [`lib/dom.js:1120`](https://github.com/xmldom/xmldom/blob/9ef2fd297ca527a05ecb11979850317a927cd20c/lib/dom.js#L1120) | `Node.prototype.isEqualNode(other)`                                                                  | ~10,000 levels           |\n\nBoth active branches (`main` and `release-0.8.x`) are identically affected. The unscoped `xmldom`\npackage (\u2264 0.6.0) carries the same recursive patterns from its initial commit.\n\n### Browser behavior\n\nTested with Chromium 147 (Playwright headless). Chromium\u0027s native C++ implementations of all\nseven DOM methods are **iterative** \u2014 they traverse the DOM without consuming JS call stack frames.\nAll seven succeed at depths up to 20,000 without any crash.\n\nWhen `@xmldom/xmldom` is bundled and run in a browser context the same recursive JS code executes\nunder the browser\u0027s V8 stack limit (~12,000\u201313,000 frames). The crash thresholds are similar to\nthose observed on Node.js 18 (~5,000 for `serializeToString`, ~10,000 for the remaining six).\n\nThe vulnerability is specific to xmldom\u0027s pure-JavaScript recursive implementation, not an\ninherent property of the DOM operations.\n\n---\n\n## PoC\n\n### `normalize()` (from @praveen-kv report, 2026-04-05)\n\n```js\nconst { DOMParser } = require(\u0027@xmldom/xmldom\u0027);\n\nfunction generateNestedXML(depth) {\n    return \u0027\u003croot\u003e\u0027 + \u0027\u003ca\u003e\u0027.repeat(depth) + \u0027text\u0027 + \u0027\u003c/a\u003e\u0027.repeat(depth) + \u0027\u003c/root\u003e\u0027;\n}\n\nconst doc = new DOMParser().parseFromString(generateNestedXML(10000), \u0027text/xml\u0027);\ndoc.documentElement.normalize();\n// RangeError: Maximum call stack size exceeded\n```\n\n### `XMLSerializer.serializeToString()` (from GHSA-2v35-w6hq-6mfw)\n\n```js\nconst { DOMParser, XMLSerializer } = require(\u0027@xmldom/xmldom\u0027);\n\nconst depth = 5000;\nconst xml = \u0027\u003ca\u003e\u0027.repeat(depth) + \u0027\u003c/a\u003e\u0027.repeat(depth);\nconst doc = new DOMParser().parseFromString(xml, \u0027text/xml\u0027);\nnew XMLSerializer().serializeToString(doc);\n// RangeError: Maximum call stack size exceeded\n```\n\nThe other methods have been verified using similar pocs.\n\n---\n\n## Impact\n\nAny service that accepts attacker-controlled XML and subsequently calls any of the seven affected\nDOM operations can be forced into a reliable denial of service with a single crafted payload.\n\nThe immediate result is an uncaught `RangeError` and failed request processing. In deployments\nwhere uncaught exceptions terminate the worker or process, the impact can extend beyond a single\nrequest and disrupt service availability more broadly.\n\nNo authentication, special options, or invalid XML is required. A valid, deeply nested XML\ndocument is enough.\n\n---\n\n## Disclosure\n\nThe `normalize()` vector was publicly disclosed at 2026-04-06T11:25:07Z via\n[xmldom/xmldom#987](https://github.com/xmldom/xmldom/pull/987) (closed without merge).\n`serializeToString()` and the five additional recursive entry points were not mentioned in that PR.\n\n---\n\n## Fix Applied\n\nAll seven affected traversals have been converted from recursive to iterative implementations, eliminating call-stack consumption on deep trees.\n\n### `walkDOM` utility\n\nA new `walkDOM(node, context, callbacks)` utility is introduced. It traverses the subtree rooted at `node` in depth-first order using an explicit JavaScript array as a stack, consuming heap memory instead of call-stack frames. `context` is an arbitrary value threaded through the walk \u2014 each `callbacks.enter(node, context)` call returns the context to pass to that node\u0027s children, enabling per-branch state (e.g. namespace snapshots in the serializer). `callbacks.exit(node, context)` (optional) is called in post-order after all children have been visited.\n\nThe following six operations are re-implemented on top of `walkDOM`:\n\n| Operation | Public entry point(s) |\n|---|---|\n| `_visitNode` helper | `getElementsByTagName()`, `getElementsByTagNameNS()`, `getElementsByClassName()`, `getElementById()` |\n| `getTextContent` inner function | `node.textContent` getter |\n| `cloneNode` module function | `Node.prototype.cloneNode(true)` |\n| `importNode` module function | `Document.prototype.importNode(node, true)` |\n| `serializeToString` worker | `XMLSerializer.prototype.serializeToString()`, `Node.prototype.toString()`, `NodeList.prototype.toString()` |\n| `normalize` | `Node.prototype.normalize()` |\n\n`normalize` uses `walkDOM` with a `null` context and an `enter` callback that merges adjacent Text children of the current node before `walkDOM` reads and queues those children \u2014 so the surviving post-merge children are what the walker descends into.\n\n### Custom iterative loop for `isEqualNode`\n\nOne function cannot use `walkDOM`:\n\n**`Node.prototype.isEqualNode(other)`** (0.9.x only; absent from 0.8.x) compares two trees in parallel. It maintains an explicit stack of `{node, other}` node pairs \u2014 one node from each tree \u2014 which cannot be expressed with `walkDOM`\u0027s single-tree visitor.\n\n### After the fix\n\nAll seven entry points succeed on trees of arbitrary depth without throwing `RangeError`. The original PoCs still demonstrate the vulnerability on unpatched versions and confirm the fix on patched versions.",
  "id": "GHSA-2v35-w6hq-6mfw",
  "modified": "2026-04-22T20:23:58Z",
  "published": "2026-04-22T20:23:57Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/security/advisories/GHSA-2v35-w6hq-6mfw"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/17678a2a73ecbd1a2da90f3d47dc23da9cef81aa"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/291257493cb0eb6980eda83b162a9c4e6d7d2597"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/2d6d6916ed8a4c223db1f6d7560ab4544c465b0f"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/430357c7b6333108856e917bf2367afe5ceb6f8a"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/4845ef109221df0890825de2822fbe77afba3afe"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/8834218c85ac2a4d757b9587c9028e67c2f7b6c3"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/8b7cfd1491314abdc347261921d7334ff15f7112"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/b0620383abc1df067f3ce1014c43ae1bc1161eeb"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/commit/e6edcab6bef5bcdba0b220bb35442aa72f452b84"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/xmldom/xmldom"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/releases/tag/0.8.13"
    },
    {
      "type": "WEB",
      "url": "https://github.com/xmldom/xmldom/releases/tag/0.9.10"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "xmldom: Uncontrolled recursion in XML serialization leads to DoS"
}

Sightings

Author	Source	Type	Date

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

Action not permitted

GHSA-2V35-W6HQ-6MFW

Summary

Details

Root cause

Node.prototype.normalize() — reported by @praveen-kv

XMLSerializer.serializeToString() — reported by @Jvr2022

Additional recursive entry points

Browser behavior

PoC

normalize() (from @praveen-kv report, 2026-04-05)

XMLSerializer.serializeToString() (from GHSA-2v35-w6hq-6mfw)

Impact

Disclosure

Fix Applied

walkDOM utility

Custom iterative loop for isEqualNode

After the fix

Tags

Sightings

Nomenclature

`Node.prototype.normalize()` — reported by @praveen-kv

`XMLSerializer.serializeToString()` — reported by @Jvr2022

`normalize()` (from @praveen-kv report, 2026-04-05)

`XMLSerializer.serializeToString()` (from GHSA-2v35-w6hq-6mfw)

`walkDOM` utility

Custom iterative loop for `isEqualNode`