Vulnerability Description
fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be forced to do an unlimited amount of entity expansion. With a very small XML input, it’s possible to make the parser spend seconds or even minutes processing a single request, effectively freezing the application. Version 5.3.6 fixes the issue. As a workaround, avoid using DOCTYPE parsing by `processEntities: false` option.
CVSS Score
HIGH
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Naturalintelligence | Fast-Xml-Parser | >= 4.1.3, < 5.3.6 |
Related Weaknesses (CWE)
References
- https://github.com/NaturalIntelligence/fast-xml-parser/commit/910dae5be2de2955e9Patch
- https://github.com/NaturalIntelligence/fast-xml-parser/releases/tag/v5.3.6ProductRelease Notes
- https://github.com/NaturalIntelligence/fast-xml-parser/security/advisories/GHSA-ExploitVendor Advisory
FAQ
What is CVE-2026-26278?
CVE-2026-26278 is a vulnerability with a CVSS score of 7.5 (HIGH). fast-xml-parser allows users to validate XML, parse XML to JS object, or build XML from JS object without C/C++ based libraries and no callback. In versions 4.1.3 through 5.3.5, the XML parser can be ...
How severe is CVE-2026-26278?
CVE-2026-26278 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-26278?
Check the references section above for vendor advisories and patch information. Affected products include: Naturalintelligence Fast-Xml-Parser.