CVE-2026-26278

Aliases:GHSA-jmr7-xgp7-cmfj
Advisory lineage Upstream: 0 Downstream: 4
Analyzed
Published: 19 Feb 2026, 19:40
Last modified:21 Jul 2026, 12:05

Vulnerability Summary

Overall Risk (default)
medium
40/100
CVSS Score
7.5 HIGH
v3.1 (cve.org)
EPSS Score
0.81% LOW
1% probability +0.78%
KEV
Not listed
Ransomware
No reports
Public exploits
1 found
Dark Web
Not detected

Timeline

19 Feb 2026, 19:40
Published
Vulnerability first disclosed
21 Jul 2026, 12:05
Last Modified
Vulnerability information updated

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 Metrics

  • v3.1•HIGH•Score: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS Trends

Current EPSS score: 0.81%• Percentile: 53%

Techniques & Countermeasures

  • CWE-776•Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

    The product uses XML documents and allows their structure to be defined with a Document Type Definition (DTD), but it does not properly control the number of recursive definitions of entities.

Affected Systems

  • naturalintelligence•fast-xml-parser

    ≥ 4.1.3, < 5.3.6 | ≥ 5.0.0, < 5.3.6 | ≥ 4.1.3, < 4.5.4

  • Npm•fast-xml-parser

    ≥ 4.1.3, < 5.3.6 | ≥ 4.1.3, < 4.5.4 | ≥ 5.0.0, < 5.3.6

References (15)