CVE-2021-33829
ckeditor4 vulnerable to cross-site scripting
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
Exploit likelihood
What each source reports
NVD Score used
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.
- Record
CVE-2021-33829- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:P/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
CVE List No score
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.
- Record
CVE-2021-33829- Updated
- 2026-11-02
EUVDEUVD-2021-1398 No score
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.
- Record
EUVD-2021-1398- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-rgx6-rjj4-c388
ckeditor4 vulnerable to cross-site scripting
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.
- Record
GHSA-rgx6-rjj4-c388- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-33829- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-33829
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.
- Record
DEBIAN-CVE-2021-33829- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
Show 6 moreShow less
OSVGHSA-rgx6-rjj4-c388
ckeditor4 vulnerable to cross-site scripting
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.
- Record
GHSA-rgx6-rjj4-c388- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Weakness
- CWE-79
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-33829
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.
- Record
UBUNTU-CVE-2021-33829- CVSS 3.1
- 6.1 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N - Updated
- 2026-11-02
OSVBIT-drupal-2021-33829 No score
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.
- Record
BIT-drupal-2021-33829- Updated
- 2026-11-02
OSVDRUPAL-CORE-2021-003 No score
Update: 2021-06-11: Added CVE-2021-33829 identifier
Drupal core uses the third-party CKEditor library. This library has an error in parsing HTML that could lead to an XSS attack. CKEditor 4.16.1 and later include the fix.
Update: 2021-06-11: More details are available on CKEditor's blog.
Users of the CKEditor library via means other than Drupal core should update their 3rd party code (e.g. the WYSIWYG module for Drupal 7). The Drupal Security Team policy is not to alert for issues affecting 3rd party libraries unless those are shipped with Drupal core. See DRUPAL-SA-PSA-2016-004 for more details.
This issue is mitigated by the fact that it only affects sites with CKEditor enabled.
- Record
DRUPAL-CORE-2021-003- Updated
- 2026-11-02
OSVUSN-5340-1 No score
ckeditor vulnerabilities
Kyaw Min Thein discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. This issue only affects Ubuntu 18.04 LTS. (CVE-2018-9861)
Micha Bentkowski discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. This issue only affects Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2020-9281)
Anton Subbotin discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. This issue only affects Ubuntu 21.10. (CVE-2021-32808)
Anton Subbotin discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to inject arbitrary code. (CVE-2021-32809)
Or Sahar discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. This issue only affects Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2021-33829)
Mika Kulmala discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. (CVE-2021-37695)
- Record
USN-5340-1- Updated
- 2026-11-02
OSVUSN-5340-2 No score
ckeditor vulnerabilities
USN-5340-1 fixed several vulnerabilities in CKEditor. This update provides the fixes for CVE-2018-9861, CVE-2020-9281, CVE-2021-32809, CVE-2021-33829 and CVE-2021-37695 for Ubuntu 16.04 ESM.
Original advisory details:
Kyaw Min Thein discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. This issue only affects Ubuntu 18.04 LTS. (CVE-2018-9861)
Micha Bentkowski discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. This issue only affects Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2020-9281)
Anton Subbotin discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. This issue only affects Ubuntu 21.10. (CVE-2021-32808)
Anton Subbotin discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to inject arbitrary code. (CVE-2021-32809)
Or Sahar discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. This issue only affects Ubuntu 18.04 LTS and Ubuntu 20.04 LTS. (CVE-2021-33829)
Mika Kulmala discovered that CKEditor incorrectly handled certain inputs. An attacker could possibly use this issue to execute arbitrary code. (CVE-2021-37695)
- Record
USN-5340-2- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
ckeditor4npm |
4.14.0 up to 4.16.1 | 4.16.1 |
drupal/corePackagist |
7.0.0 up to 7.80 | 7.80 |
drupal/corePackagist |
8.0.0 up to 8.9.16 | 8.9.16 |
drupal/corePackagist |
9.0.0 up to 9.0.14 | 9.0.14 |
drupal/corePackagist |
9.1.0 up to 9.1.9 | 9.1.9 |
drupal/drupalPackagist |
7.0.0 up to 7.80 | 7.80 |
drupal/drupalPackagist |
8.0.0 up to 8.9.16 | 8.9.16 |
drupal/drupalPackagist |
9.0.0 up to 9.0.14 | 9.0.14 |
drupal/drupalPackagist |
9.1.0 up to 9.1.9 | 9.1.9 |
drupalBitnami |
8.9.0 up to 8.9.16, 9.0.0 up to 9.0.14, 9.1.0 up to 9.1.9 | 8.9.169.0.149.1.9 |
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| Package | Affected | Fixed |
|---|---|---|
ckeditorDebian:12 |
before 4.16.0+dfsg-2 | 4.16.0+dfsg-2 |
ckeditor3Debian:12 |
All versions, plus listed versions 3.6.6.1+dfsg-7 |
None known |
ckeditorDebian:9 From an advisory covering 2 CVEs |
before 4.5.7+dfsg-2+deb9u1, plus listed versions 4.5.7+dfsg-2 |
4.5.7+dfsg-2+deb9u1 |
drupal/corePackagist |
8.0.0 up to 8.9.16, 9.0.0 up to 9.0.14, 9.1.0 up to 9.1.9, plus listed versions 8.0.18.0.28.0.38.0.48.0.5 Show 45 moreShow less8.0.68.1.08.1.0-beta18.1.0-beta28.1.0-rc18.1.18.1.108.1.28.1.38.1.48.1.58.1.68.1.78.1.88.1.98.2.08.2.0-beta18.2.0-beta28.2.0-beta38.2.0-rc18.2.0-rc28.2.18.2.28.2.38.2.48.2.58.2.68.2.78.2.88.3.08.3.0-alpha18.3.0-beta18.3.0-rc18.3.0-rc28.3.18.3.28.3.38.3.48.3.58.3.68.3.78.3.88.3.98.4.08.4.0-alpha1 |
8.9.169.0.149.1.9 |
drupal/corePackagist |
8.0.0 up to 8.9.16, plus listed versions 8.0.18.0.28.0.38.0.48.0.5 Show 45 moreShow less8.0.68.1.08.1.0-beta18.1.0-beta28.1.0-rc18.1.18.1.108.1.28.1.38.1.48.1.58.1.68.1.78.1.88.1.98.2.08.2.0-beta18.2.0-beta28.2.0-beta38.2.0-rc18.2.0-rc28.2.18.2.28.2.38.2.48.2.58.2.68.2.78.2.88.3.08.3.0-alpha18.3.0-beta18.3.0-rc18.3.0-rc28.3.18.3.28.3.38.3.48.3.58.3.68.3.78.3.88.3.98.4.08.4.0-alpha1 |
8.9.16 |
drupal/corePackagist |
9.0.0 up to 9.0.14, plus listed versions 9.0.19.0.109.0.119.0.129.0.13 Show 8 moreShow less9.0.29.0.39.0.49.0.59.0.69.0.79.0.89.0.9 |
9.0.14 |
drupal/corePackagist |
9.1.0 up to 9.1.9, plus listed versions 9.1.19.1.29.1.39.1.49.1.59.1.69.1.79.1.8 |
9.1.9 |
drupal/drupalPackagist |
8.0.0 up to 8.9.16, plus listed versions 8.0.18.0.28.0.38.0.48.0.5 Show 45 moreShow less8.0.68.1.08.1.0-beta18.1.0-beta28.1.0-rc18.1.18.1.108.1.28.1.38.1.48.1.58.1.68.1.78.1.88.1.98.2.08.2.0-beta18.2.0-beta28.2.0-beta38.2.0-rc18.2.0-rc28.2.18.2.28.2.38.2.48.2.58.2.68.2.78.2.88.3.08.3.0-alpha18.3.0-beta18.3.0-rc18.3.0-rc28.3.18.3.28.3.38.3.48.3.58.3.68.3.78.3.88.3.98.4.08.4.0-alpha1 |
8.9.16 |
drupal/drupalPackagist |
9.0.0 up to 9.0.14, plus listed versions 9.0.19.0.109.0.119.0.129.0.13 Show 8 moreShow less9.0.29.0.39.0.49.0.59.0.69.0.79.0.89.0.9 |
9.0.14 |
drupal/drupalPackagist |
9.1.0 up to 9.1.9, plus listed versions 9.1.19.1.29.1.39.1.49.1.59.1.69.1.79.1.8 |
9.1.9 |
ckeditorUbuntu:Pro:16.04:LTS |
before 4.5.7+dfsg-2ubuntu0.16.04.1~esm1, plus listed versions 4.4.4+dfsg1-34.5.6+dfsg-14.5.7+dfsg-14.5.7+dfsg-2 |
4.5.7+dfsg-2ubuntu0.16.04.1~esm1 |
ckeditorUbuntu:18.04:LTS |
before 4.5.7+dfsg-2ubuntu0.18.04.1, plus listed versions 4.5.7+dfsg-2 |
4.5.7+dfsg-2ubuntu0.18.04.1 |
ckeditorUbuntu:20.04:LTS |
before 4.12.1+dfsg-1ubuntu0.1, plus listed versions 4.11.1+dfsg-14.12.1+dfsg-1 |
4.12.1+dfsg-1ubuntu0.1 |
ckeditorUbuntu:18.04:LTS From an advisory covering 6 CVEs |
before 4.5.7+dfsg-2ubuntu0.18.04.1, plus listed versions 4.5.7+dfsg-2 |
4.5.7+dfsg-2ubuntu0.18.04.1 |
ckeditorUbuntu:20.04:LTS From an advisory covering 6 CVEs |
before 4.12.1+dfsg-1ubuntu0.1, plus listed versions 4.11.1+dfsg-14.12.1+dfsg-1 |
4.12.1+dfsg-1ubuntu0.1 |
ckeditorUbuntu:Pro:16.04:LTS From an advisory covering 5 CVEs |
before 4.5.7+dfsg-2ubuntu0.16.04.1~esm1, plus listed versions 4.4.4+dfsg1-34.5.6+dfsg-14.5.7+dfsg-14.5.7+dfsg-2 |
4.5.7+dfsg-2ubuntu0.16.04.1~esm1 |
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| Nuclei | Drupal 7 CKEditor XSS |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, Nuclei, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-33829 is a medium vulnerability (CVSS 6.1) in Ckeditor, published May 26, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.19%, the 88th percentile. Fixed in ckeditor4 4.16.1.
References
drupal.org/sa-core-2021-003
ckeditor.com/blog/ckeditor-4.16.1-with-accessibility-enhancements
lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/NYA354LJP47KCVJMTUO77ZCX3ZK42G3T
lists.debian.org/debian-lts-announce/2021/11/msg00007.html
Show 20 moreShow less
nvd.nist.gov/vuln/detail/CVE-2021-33829
npmjs.com/package/ckeditor4
github.com/FriendsOfPHP/security-advisories/blob/master/drupal/core/CVE-2021-33829.yaml
security-tracker.debian.org/tracker/CVE-2021-33829
ubuntu.com/security/CVE-2021-33829
cve.org/CVERecord?id=CVE-2021-33829
Left out here: 348 versions. The JSON record has them.