Inefficient Algorithmic Complexity Affecting fast-xml-parser package, versions <5.12.0
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-JS-FASTXMLPARSER-22409021
- published11 Nov 2026
- disclosed10 Nov 2026
- creditSai Prapanch.H
Introduced: 10 Nov 2026
NewCVE-2026-126066 (opens in a new tab)How to fix?
Upgrade fast-xml-parser to version 5.12.0 or higher.
Overview
fast-xml-parser is a Validate XML, Parse XML, Build XML without C/C++ based libraries
Affected versions of this package are vulnerable to Inefficient Algorithmic Complexity in the readStopNodeData() function in OrderedObjParser.js. An attacker can block the event loop by supplying XML in which a stop node body contains many <a fragments and no closing >, which makes the function rescan the entire remaining input from every <. This affects only applications that set the non-default stopNodes option to match an element in the parsed document.