High severity · published Aug 13, 2026
CVE-2026-73569
fast-xml-parser: Repeated DOCTYPE declarations reset entity expansion limits
8.7
CVSS
0.5%
EPSS
No
On KEV
Description
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.
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 43% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
FA
fast-xml-parser · NaturalIntelligence
>= 5.9.3, < 5.10.1 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-73569
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-73569
github.com
https://github.com/NaturalIntelligence/fast-xml-parser/commit/4e546e03987662de5495d050b5fba26bea65383f
github.com
https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.10.1
github.com
https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-8r6m-32jq-jx6q
More from fast-xml-parser
9.3
CVE-2026-25896
fast-xml-parser has an entity encoding bypass via regex injection in DOCTYPE entity names
7.5
CVE-2026-33036
fast-xml-parser affected by numeric entity expansion bypassing all entity expansion limits (incomplete fix for CVE-2026-26278)
7.5
CVE-2026-27942
fast-xml-parser has stack overflow in XMLBuilder with preserveOrder
7.5
CVE-2026-26278
fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)
7.5
CVE-2026-25128
fast-xml-parser has RangeError DoS Numeric Entities Bug