CVE-2026-73569 fast-xml-parser: Repeated DOCTYPE declarations reset entity expansion limits
A crafted XML document can cause excessive CPU and memory usage in fast-xml-parser by resetting entity expansion limits, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-73569?
CVE-2026-73569 is a high-severity denial of service vulnerability in NaturalIntelligence fast-xml-parser, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-776
Which versions are affected by CVE-2026-73569?
2 open source packages ship an affected version, including fast-xml-parser.
| Package | Affected | Fixed in |
|---|---|---|
fast-xml-parser npm | From 5.9.3 | 5.10.1 |
fast-xml-parser npm | From 5.9.3 | 5.10.1 |
How do I fix CVE-2026-73569?
Upgrade fast-xml-parser to 5.10.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-73569 being exploited?
There is no known exploitation of CVE-2026-73569 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-73569, GHSA-8r6m-32jq-jx6q, UBUNTU-CVE-2026-73569.