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High severityNVD Advisory· Published Feb 19, 2026· Updated Mar 2, 2026

fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)

CVE-2026-26278

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.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
fast-xml-parsernpm
>= 4.1.3, < 4.5.44.5.4
fast-xml-parsernpm
>= 5.0.0, < 5.3.65.3.6

Affected products

34

Patches

Vulnerability mechanics

References

5

News mentions

0

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