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CVE-2026-25896
February 20, 2026
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. From 4.1.3to before 5.3.5, a dot (.) in a DOCTYPE entity name is treated as a regex wildcard during entity replacement, allowing an attacker to shadow built-in XML entities (<, >, &, ", ') with arbitrary values. This bypasses entity encoding and leads to XSS when parsed output is rendered. This vulnerability is fixed in 5.3.5.
Affected Packages
https://github.com/NaturalIntelligence/fast-xml-parser.git (GITHUB):
Affected version(s) >=v4.1.3 <v5.3.5
Fix Suggestion:
Update to version v5.3.5
fast-xml-parser (NPM):
Affected version(s) >=4.1.3 <4.5.4
Fix Suggestion:
Update to version 4.5.4
fast-xml-parser (NPM):
Affected version(s) >=5.0.0 <5.3.5
Fix Suggestion:
Update to version 5.3.5
Additional Notes
The description of this vulnerability differs from MITRE.
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CVSS v4
Base Score:
9.2
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
NONE
User Interaction
NONE
Vulnerable System Confidentiality
LOW
Vulnerable System Integrity
HIGH
Vulnerable System Availability
NONE
Subsequent System Confidentiality
LOW
Subsequent System Integrity
HIGH
Subsequent System Availability
NONE
CVSS v3
Base Score:
9.3
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality
LOW
Integrity
HIGH
Availability
NONE
Weakness Type (CWE)
Incorrect Regular Expression
EPSS
Base Score:
0.04