CVE-2026-27942: Naturalintelligence Fast-XML-Parser

High severity, CVSS 7.5. EPSS: 0.7% 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. Prior to version 5.3.8, the application crashes with stack overflow when user use XML builder with `preserveOrder:true`. Version 5.3.8 fixes the issue. As a workaround, use XML builder with `preserveOrder:false` or check the input data before passing to builder.

Affected products

• Naturalintelligence Fast-XML-Parser: before 4.5.4 (fixed in 4.5.4); from 5.0.0, before 5.3.8 (fixed in 5.3.8)

Published 2026-02-26. Last modified 2026-06-17.