CVE-2026-26278

fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)

Published Feb 19, 2026 CVSS 3.1 · 7.5 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-jmr7-xgp7-cmfj fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)
History
Type Values Removed Values Added
CPEs cpe:2.3:a:naturalintelligence:fast-xml-parser:*:*:*:*:*:*:*:*
Type Values Removed Values Added
First Time appeared Naturalintelligence
Naturalintelligence fast-xml-parser
Vendors & Products Naturalintelligence
Naturalintelligence fast-xml-parser
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
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.
Title fast-xml-parser affected by DoS through entity expansion in DOCTYPE (no expansion limit)
Weaknesses CWE-776
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Sep 10, 2026, 12:05 PM
Reserved
Feb 12, 2026, 5:10 PM
Status
Modified
Published
Feb 19, 2026, 8:25 PM
Modified
Sep 10, 2026, 1:17 PM
Severity
Important
Public date
Feb 19, 2026, 7:40 PM