CVE-2026-26278

HIGH

fast-xml-parser 4.1.3-5.3.5 - XML External Entity Injection via Unrestricted Entity Expansion

Title source: llm
STIX 2.1

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.

References (13)

Core 13
Core References

Scores

CVSS v3 7.5
EPSS 0.0084
EPSS Percentile 54.3%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CISA SSVC

Vulnrichment
Exploitation none
Automatable yes
Technical Impact partial

Details

CWE
CWE-776
Status published
Products (4)
naturalintelligence/fast-xml-parser 4.1.3 - 5.3.6
NaturalIntelligence/fast-xml-parser >= 4.1.3, < 4.5.4
NaturalIntelligence/fast-xml-parser >= 5.0.0, < 5.3.6
npm/fast-xml-parser 4.1.3 - 4.5.4npm
Published Feb 19, 2026
Tracked Since Feb 19, 2026