Excessive CPU Use in fast-xml-parser Due to Multiple DOCTYPE Declarations
CVE-2026-73569

8.7HIGH

Key Information:

Vendor

Naturalintelligence

Status
Fast-xml-parser
Vendor
CVE Published:
13 August 2026

What is CVE-2026-73569?

The fast-xml-parser library has a vulnerability that allows for excessive CPU consumption and memory issues during the parsing of specially crafted XML documents. When multiple DOCTYPE declarations are processed, the entity expansion limits can be reset repeatedly. This behavior may lead to significant resource exhaustion, potentially causing event-loop blocking and process termination. The vulnerability affects versions 5.9.3 through 5.10.1, but it has been addressed in version 5.10.1.

Affected Version(s)

fast-xml-parser >= 5.9.3, < 5.10.1

References

https://github.com/NaturalIntelligence/fast-xml-parser/se...
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https://github.com/NaturalIntelligence/fast-xml-parser/co...
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https://github.com/NaturalIntelligence/fast-xml-parser/re...
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CVSS V4

Score:
8.7
Severity:
HIGH
Confidentiality:
None
Integrity:
None
Availability:
High
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.