CVE-2021-40440Network attack vector

Authenticated script execution via undisclosed XSS flaw

Published Sep 15, 2021 · Updated Aug 10, 2026

Cross-site scripting in Microsoft Dynamics 365 Business Central allows remote authenticated users to execute script after user interaction. Microsoft has not published the affected page, parameter, input source, or output-encoding operation that mishandles untrusted content. Exploitation requires low-privileged access and user interaction; successful script execution can read or alter data in the affected browser context, with no availability impact.

CVSS severity5.4
Medium
EPSS probability1.05%
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 Microsoft Dynamics 365 Business Central allows remote authenticated users to execute script after user interaction. Microsoft has not published the affected page, parameter, input source, or output-encoding operation that mishandles untrusted content. Exploitation requires low-privileged access and user interaction; successful script execution can read or alter data in the affected browser context, with no availability impact.

The record

CVE
CVE-2021-40440
Published
Sep 15, 2021
Updated
Aug 10, 2026
Vendor
Microsoft
Product
Microsoft Dynamics 365 Business Central 2020 Release Wave 2 (On-Premise)
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Sep 15, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 10, 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=17.0.0.0 <17.0.29460

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Microsoft · Microsoft Dynamics 365 Business Central 2020 Release Wave 2 (On-Premise)version=17.0.0.0 <17.0.29460
Microsoft · Microsoft Dynamics 365 Business Central 2021 Release Wave 1version=18.0.0.0 <18.0.29486

Published CVSS scores

5.4Microsoft CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

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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