CVE-2026-26278

HIGH

7.5

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.

CVE Details

CVSS v3.1 Score7.5

SeverityHIGH

CVSS VectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack VectorNETWORK

ComplexityLOW

Privileges RequiredNONE

User InteractionNONE

Published2/19/2026

Last Modified2/23/2026

Sourcenvd

Honeypot Sightings0

Affected Products

naturalintelligence:fast-xml-parser

Weaknesses (CWE)

CWE-776

References

https://github.com/NaturalIntelligence/fast-xml-parser/commit/910dae5be2de2955e968558fadf6e8f74f117a77(security-advisories@github.com)

https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.6(security-advisories@github.com)

https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-jmr7-xgp7-cmfj(security-advisories@github.com)

IOC Correlations

No correlations recorded

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