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Fencer Vulns
medium 6.1

CVE-2021-33829 json

ckeditor4 vulnerable to cross-site scripting

published 2021-05-26 5 y ago modified 2026-09-19 50 d ago also BIT-drupal-2021-33829 , DRUPAL-CORE-2021-003 , EUVD-2021-1398 , GHSA-rgx6-rjj4-c388

cvss
6.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.2%
EPSS 3.2% chance of exploitation in 30 days, percentile 88%
public exploits
0
none known, plus a Nuclei check

Summary

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.

Patch / fix

  • npm ckeditor4 4.16.1
  • packagist drupal/core 7.80, 8.9.16, 9.0.14, 9.1.9
  • packagist drupal/drupal 7.80, 8.9.16, 9.0.14, 9.1.9
  • bitnami drupal 8.9.16, 9.0.14, 9.1.9
  • ckeditor ckeditor 4.16.1
  • drupal drupal 8.9.16, 9.0.14, 9.1.9
  • ckeditor Debian 12 4.16.0+dfsg-2

debian advisories DEBIAN-CVE-2021-33829

  • ckeditor Ubuntu 18.04 LTS 4.5.7+dfsg-2ubuntu0.18.04.1
  • ckeditor Ubuntu 20.04 LTS 4.12.1+dfsg-1ubuntu0.1
  • ckeditor Ubuntu Pro 16.04 LTS 4.5.7+dfsg-2ubuntu0.16.04.1~esm1

ubuntu advisories UBUNTU-CVE-2021-33829

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • drupal Arch Linux 9.1.10-1

arch linux advisories AVG-2069

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-33829 updated cvss 6.1

ckeditor: cross-site scripting allows remote attackers to inject executable JavaScript code

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

3.19% chance of exploitation in the next 30 days, higher than 88% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

CVSS scores

assigned by version score vector
GitHub 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:N/I:P/A:N
OSV 3.1 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Affected packages

ecosystem package affected fixed in
npm ckeditor4
>=4.14.0, <4.16.1
4.16.1
packagist drupal/core
>=7.0.0, <7.80
>=8.0.0, <8.9.16
>=9.0.0, <9.0.14
>=9.1.0, <9.1.9
7.80
8.9.16
9.0.14
9.1.9
packagist drupal/drupal
>=7.0.0, <7.80
>=8.0.0, <8.9.16
>=9.0.0, <9.0.14
>=9.1.0, <9.1.9
7.80
8.9.16
9.0.14
9.1.9
bitnami drupal
>=8.9.0, <8.9.16
>=9.0.0, <9.0.14
>=9.1.0, <9.1.9
8.9.16
9.0.14
9.1.9

Classification

Weakness
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.