XML Entity Expansion in fast-xml-parser - CVE-2026-73569
Published: November 4, 2026
Vulnerability identifier: #VU159255
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: CVE-2026-73569
CWE-ID: CWE-776
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service through excessive CPU consumption, event-loop blocking, memory exhaustion, or process termination.
The vulnerability exists due to improper enforcement of XML entity expansion limits in fast-xml-parser and the addInputEntities() function of @nodable/entities when processing multiple DOCTYPE declarations within a single XML document. A remote attacker can supply a crafted XML document containing repeated DOCTYPE declarations to reset the maxTotalExpansions and maxExpandedLength counters during parsing, exceed the configured limits, and cause a denial of service.
Affected software
fast-xml-parser
How to mitigate CVE-2026-73569
Install security update from vendor's website.
fast-xml-parser - update to 5.10.1