CVE-2026-26278

7.5 highEPSS 0.9%

High (7.5) in naturalintelligence fast-xml-parser. EPSS 0.9% chance of exploitation in the next 30 days. Fixed in fast-xml-parser 4.5.4, 5.3.6.

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.

Severity

CVSS 3.1

7.5 high

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.9% chance of exploitation in the next 30 days; higher than 60% of CVEs (scores of 2026-10-31)
CWE: CWE-776
Published: 2026-02-19
Modified: 2026-09-10
Record from: the NVD, synced 2026-10-19

Affected

naturalintelligence:fast-xml-parser

Packages (OSV)

Advisory	Ecosystem	Package	Affected	Fixed in
GHSA-jmr7-xgp7-cmfj	npm	fast-xml-parser	>=4.1.3 <4.5.4	4.5.4
GHSA-jmr7-xgp7-cmfj	npm	fast-xml-parser	>=5.0.0 <5.3.6	5.3.6

References

Check your stack JSON