Vulnerability Details CVE-2026-33036
fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. Versions 4.0.0-beta.3 through 5.5.5 contain a bypass vulnerability where numeric character references (&#NNN;, &#xHH;) and standard XML entities completely evade the entity expansion limits (e.g., maxTotalExpansions, maxExpandedLength) added to fix CVE-2026-26278, enabling XML entity expansion Denial of Service. The root cause is that replaceEntitiesValue() in OrderedObjParser.js only enforces expansion counting on DOCTYPE-defined entities while the lastEntities loop handling numeric/standard entities performs no counting at all. An attacker supplying 1M numeric entity references like A can force ~147MB of memory allocation and heavy CPU usage, potentially crashing the process—even when developers have configured strict limits. This issue has been fixed in version 5.5.6.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 11.1%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-33036
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.10
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.11
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.12
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.13
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.14
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.15
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.2
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.3
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.4
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.5
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.6
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.7
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.8
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.0.9
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.1.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.1.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.1.2
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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
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.5.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.5.2
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cpe:2.3:a:naturalintelligence:fast-xml-parser:4.5.3
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.2
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.3
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.4
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.5
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.6
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.7
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.8
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.0.9
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.1.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.2.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.2.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.2.2
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.2.3
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.2.4
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.2.5
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.3.0
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.3.1
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.3.2
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.3.3
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.3.4
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.3.5
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.3.6
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cpe:2.3:a:naturalintelligence:fast-xml-parser:5.3.7