CVE-2026-26278

High

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. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the application. Version 5.3.6 fixes the issue. As a workaround, avoid using DOCTYPE parsing by `processEntities: false` option.

SeverityHigh

CVSS7.5

Exploit probability—

ProductNaturalintelligence Fast-xml-parser

PublishedFeb 19, 2026

First seenFeb 19, 2026

Weakness typeCWE-776CWE-776

How to fix

Update

naturalintelligence fast-xml-parser5.3.6 or later
fast-xml-parser4.5.4, 5.3.6 or later

Vendor advisories

Affected products

Product	Affected versions	Fixed in
naturalintelligence fast-xml-parser	4.1.3 ≤ v < 5.3.6	5.3.6
fast-xml-parsernpm	4.1.3 ≤ v < 4.5.4, 5.0.0 ≤ v < 5.3.6	4.5.4, 5.3.6

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