Bug 2515526 (CVE-2026-73569)

Summary:	CVE-2026-73569 fast-xml-parser: fast-xml-parser: Denial of Service via repeated DOCTYPE declarations
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	abarbaro, abuckta, alizardo, anjoseph, dkeler, dkuc, dschmidt, ewittman, janstey, jchui, jhe, jlanda, jprabhak, kshier, ktsao, nboldt, nipatil, oaljalju, orabin, pantinor, psrna, rjohnson, rkubis, simaishi, stcannon, suppawar, teagle, thason, wtam, yguenane
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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Doc Text:	A flaw was found in fast-xml-parser. A remote attacker could exploit this by submitting a specially crafted XML document containing multiple DOCTYPE declarations. These repeated declarations can reset internal entity expansion limits during parsing. This can lead to excessive CPU usage, event-loop blocking, and memory exhaustion, ultimately resulting in a Denial of Service (DoS) for the application processing the XML.	Story Points:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-08-13 18:26:30 UTC

fast-xml-parser allows users to process XML from JS object without C/C++ based libraries or callbacks. From 5.9.3 until 5.10.1, src/xmlparser/OrderedObjParser.js processes multiple DOCTYPE declarations within a single XML document and passes each declaration's entities through addInputEntities(). addInputEntities() resets maxTotalExpansions and maxExpandedLength every time it is called, allowing additional DOCTYPE declarations to repeatedly reset the configured entity-expansion limits during one parse operation. A crafted XML document can then cause excessive CPU use, event-loop blocking, memory exhaustion, and process termination. This issue is fixed in version 5.10.1.