CVE-2026-44665Public exploitNetwork attack vector

Markup attribute injection via unescaped quotes

Published May 13, 2026 · Updated May 13, 2026

XML attribute injection in Natural Intelligence fast-xml-builder before 1.1.7 allows attackers to add XML or HTML attributes via crafted JSON. With processEntities disabled, the builder fails to escape a quote inside an @_ attribute value, so the quote ends that value and trailing text becomes new attributes. Any application that passes attacker-controlled JSON into this configuration can emit attacker-chosen markup attributes, including event handlers.

CVSS severity8.7
High
EPSS probability0.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

XML attribute injection in Natural Intelligence fast-xml-builder before 1.1.7 allows attackers to add XML or HTML attributes via crafted JSON. With processEntities disabled, the builder fails to escape a quote inside an @_ attribute value, so the quote ends that value and trailing text becomes new attributes. Any application that passes attacker-controlled JSON into this configuration can emit attacker-chosen markup attributes, including event handlers.

The record

CVE
CVE-2026-44665
Published
May 13, 2026
Updated
May 13, 2026
Vendor
Natural Intelligence
Product
fast-xml-builder
Classifications
CWE-91, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 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=< 1.1.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Natural Intelligence · fast-xml-builderversion=< 1.1.7

Published CVSS scores

8.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
6.1GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-91XML Injection (aka Blind XPath Injection)
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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