Vulnerability Details CVE-2026-26278
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 15.2%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-26278
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.1.3
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.1.4
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.2.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.2.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.2.2
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.2.3
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.2.4
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.2.5
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.2.6
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.2.7
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.3.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.3.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.3.2
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.3.3
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.3.4
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.3.5
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.3.6
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.4.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.4.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.5.0