CVE-2021-42227Public exploitNetwork attack vector

Stored XSS via unrestricted HTML file upload

Published Oct 14, 2021 · Updated Aug 4, 2024

Stored XSS in KindEditor 4.1.x allows remote attackers to execute script in a user's browser through an uploaded HTML file. The upload_json.php endpoint accepts an imgFile with an .html filename and text/html content, storing attacker-controlled script as a web page. Submission requires no privileges, but a user must load the stored page before the script executes in that site's origin.

CVSS severity6.1
Medium
EPSS probability0.94%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in KindEditor 4.1.x allows remote attackers to execute script in a user's browser through an uploaded HTML file. The upload_json.php endpoint accepts an imgFile with an .html filename and text/html content, storing attacker-controlled script as a web page. Submission requires no privileges, but a user must load the stored page before the script executes in that site's origin.

The record

CVE
CVE-2021-42227
Published
Oct 14, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-79, CAPEC-592, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

6.1GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
6.1NIST NVDCVSS: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.

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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CAPEC-592Stored XSS
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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