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Vulnerability record · CVE-2021-33829 · published 9 June 2021

CVE-2021-33829: Ckeditor cross-site scripting vulnerability

Ckeditor · Ckeditor

A cross-site scripting (XSS) vulnerability in the HTML Data Processor in CKEditor 4 4.14.0 through 4.16.x before 4.16.1 allows remote attackers to inject executable JavaScript code through a crafted comment because --!> is mishandled.

6.1 CVSS 3.1 Medium EPSS 3.2% · top 12.4% CWE-79 · Cross-site scripting
6.1CVSS 3.1 base score, v2 4.3
3.2%EPSS exploitation probability, 30 days
NoNot in CISA KEV
4Affected product versions listed by NVD
12References
17 Jun 2026Last modified by NVD

Description

A cross-site scripting (XSS) vulnerability in the HTML Data Processor in CKEditor 4 4.14.0 through 4.16.x before 4.16.1 allows remote attackers to inject executable JavaScript code through a crafted comment because --!> is mishandled.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected products

4 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://ckeditor.com/blog/ckeditor-4.16.1-with-accessibility-enhancements/#improvements-for-comments-in-html-parser PatchRelease NotesVendor Advisory
https://lists.debian.org/debian-lts-announce/2021/11/msg00007.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NYA354LJP47KCVJMTUO77ZC
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UVOYN2WKDPLKCNILIGEZM23
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WAGNWHFIQAVCP537KFFS2A2
https://www.drupal.org/sa-core-2021-003 PatchThird Party Advisory
https://ckeditor.com/blog/ckeditor-4.16.1-with-accessibility-enhancements/#improvements-for-comments-in-html-parser PatchRelease NotesVendor Advisory
https://lists.debian.org/debian-lts-announce/2021/11/msg00007.html Mailing ListThird Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NYA354LJP47KCVJMTUO77ZC
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UVOYN2WKDPLKCNILIGEZM23
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WAGNWHFIQAVCP537KFFS2A2
https://www.drupal.org/sa-core-2021-003 PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-33829), CISA KEV, FIRST EPSS (scores of 2026-09-29). This page is refreshed as NVD updates the record.