CVE-2026-25896

Critical

Description

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. From 4.1.3to before 5.3.5, a dot (.) in a DOCTYPE entity name is treated as a regex wildcard during entity replacement, allowing an attacker to shadow built-in XML entities (<, >, &, ", ') with arbitrary values. This bypasses entity encoding and leads to XSS when parsed output is rendered. This vulnerability is fixed in 5.3.5.

SeverityCritical

CVSS9.3

Exploit probability—

ProductNaturalintelligence Fast-xml-parser

PublishedFeb 20, 2026

First seenFeb 20, 2026

Weakness typeCWE-185CWE-185

How to fix

Update

naturalintelligence fast-xml-parser5.3.5 or later
fast-xml-parser5.3.5, 4.5.4 or later

Vendor advisories

Affected products

Product	Affected versions	Fixed in
naturalintelligence fast-xml-parser	4.1.3 ≤ v < 5.3.5	5.3.5
fast-xml-parsernpm	5.0.0 ≤ v < 5.3.5, 4.1.3 ≤ v < 4.5.4	5.3.5, 4.5.4

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