GHSA-37qj-frw5-hhjh — fast-xml-parser has RangeError DoS Numeric Entities Bug

Affected: npm: fast-xml-parser

### Summary A RangeError vulnerability exists in the numeric entity processing of fast-xml-parser when parsing XML with out-of-range entity code points (e.g., `&#9999999;` or `&#xFFFFFF;`). This causes the parser to throw an uncaught exception, crashing any application that processes untrusted XML input.

### Details The vulnerability exists in `/src/xmlparser/OrderedObjParser.js` at lines 44-45:

```javascript "num_dec": { regex: /&#([0-9]{1,7});/g, val : (_, str) => String.fromCodePoint(Number.parseInt(str, 10)) }, "num_hex": { regex: /&#x([0-9a-fA-F]{1,6});/g, val : (_, str) => String.fromCodePoint(Number.parseInt(str, 16)) }, ```

The `String.fromCodePoint()` method throws a `RangeError` when the code point exceeds the valid Unicode range (0 to 0x10FFFF / 1114111). The regex patterns can capture values far exceeding this: - `[0-9]{1,7}` matches up to 9,999,999 - `[0-9a-fA-F]{1,6}` matches up to 0xFFFFFF (16,777,215)

The entity replacement in `replaceEntitiesValue()` (line 452) has no try-catch:

```javascript val = val.replace(entity.regex, entity.val); ```

This causes the RangeError to propagate uncaught, crashing the parser and any application using it. ### PoC #### Setup

Create a directory with these files:

``` poc/ ├── package.json ├── server.js ```

**package.json** ```json { "dependencies": { "fast-xml-parser": "^5.3.3" } } ```

**server.js** ```javascript const http = require('http'); const { XMLParser } = require('fast-xml-parser');

const parser = new XMLPar…

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GHSA-37qj-frw5-hhjh — fast-xml-parser has RangeError DoS Numeric Entities Bug