CVE-2026-25896Public exploitNetwork attack vector

Cross-site scripting via wildcard DOCTYPE entity replacement

Published Feb 20, 2026 · Updated Feb 20, 2026

Cross-site scripting in fast-xml-parser 4.1.3 through 4.5.3 and 5.0.0 through 5.3.4 allows remote attackers to inject script. DocTypeReader.js and OrderedObjParser.js pass DOCTYPE entity names directly into RegExp(), so a dot matches characters in built-in entity references and substitutes attacker-controlled text before built-ins are decoded. Default entity processing is sufficient; XSS occurs when an application parses attacker-supplied XML and renders the resulting value into HTML.

CVSS severity9.3
Critical
EPSS probability0.46%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site scripting in fast-xml-parser 4.1.3 through 4.5.3 and 5.0.0 through 5.3.4 allows remote attackers to inject script. DocTypeReader.js and OrderedObjParser.js pass DOCTYPE entity names directly into RegExp(), so a dot matches characters in built-in entity references and substitutes attacker-controlled text before built-ins are decoded. Default entity processing is sufficient; XSS occurs when an application parses attacker-supplied XML and renders the resulting value into HTML.

The record

CVE
CVE-2026-25896
Published
Feb 20, 2026
Updated
Feb 20, 2026
Vendor
Natural Intelligence
Product
fast-xml-parser
Classifications
CWE-79, CWE-185, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 20, 2026CVE publishedPublication date reported by the CVE source.
  2. Feb 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 4.1.3, < 5.3.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Natural Intelligence · fast-xml-parserversion=>= 4.1.3, < 5.3.5

Published CVSS scores

9.3GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-185Incorrect Regular Expression
T1203Exploitation for Client Execution

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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