Bug 2441120 (CVE-2026-26278)

Summary: CVE-2026-26278 fast-xml-parser: fast-xml-parser: Denial of Service via unlimited XML entity expansion
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedCC: abarbaro, abuckta, alizardo, anjoseph, anthomas, caswilli, dkuc, dschmidt, ehelms, erezende, fdeutsch, ggainey, jchui, jhe, jlanda, jprabhak, juwatts, kaycoth, kshier, ktsao, manissin, mattdavi, mhulan, nboldt, nmoumoul, orabin, oramraz, osousa, pcreech, psrna, rchan, rjohnson, simaishi, smallamp, smcdonal, smullick, stcannon, stirabos, teagle, thason, tmalecek, wtam, yguenane
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A denial of service flaw was found in fast-xml-parser. A remote attacker can exploit this vulnerability by providing a specially crafted, small XML input. This input can force the XML parser to perform an unlimited amount of entity expansion, consuming excessive resources. This can lead to the application freezing for an extended period, resulting in a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2441130, 2441131    
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Description OSIDB Bzimport 2026-02-19 21:03:56 UTC 
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.