Summary
fast-xml-parser: Repeated DOCTYPE declarations reset entity expansion limits
Workarounds
- Manually check if multiple DOCTYPEs are not present in input contents
- Update to v5.10.1
- Keep
processEntityflag off
Impact
fast-xml-parser processes multiple "DOCTYPE" declarations within a single XML document. Each declaration passes its entities to @nodable/entities through addInputEntities().
addInputEntities() resets the entity expansion counters every time it is called. An attacker can therefore insert additional DOCTYPE declarations to repeatedly reset maxTotalExpansions and maxExpandedLength during one parse operation.
This allows a crafted XML document to exceed the configured entity-expansion limits and can cause excessive CPU use, event-loop blocking, memory exhaustion, and process termination.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-73569? CVE-2026-73569 is a high-severity security vulnerability in fast-xml-parser (npm), affecting versions >= 5.9.3, < 5.10.1. It is fixed in 5.10.1.
- Which versions of fast-xml-parser are affected by CVE-2026-73569? fast-xml-parser (npm) versions >= 5.9.3, < 5.10.1 is affected.
- Is there a fix for CVE-2026-73569? Yes. CVE-2026-73569 is fixed in 5.10.1. Upgrade to this version or later.
- Is CVE-2026-73569 exploitable, and should I be worried? Whether CVE-2026-73569 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-73569 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-73569? Upgrade
fast-xml-parserto 5.10.1 or later.