CVE-2026-25128: Naturalintelligence Fast-XML-Parser

High severity, CVSS 7.5. EPSS: 0.6% chance of exploitation in the next 30 days.

fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 5.0.9 through 5.3.3, 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. Version 5.3.4 fixes the issue.

Affected products

Naturalintelligence Fast-XML-Parser: from 5.0.9, before 5.3.4 (fixed in 5.3.4)

Published 2026-01-30. Last modified 2026-06-17.