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Vulnerability details: VCID-s8u8-xbdk-87dj
Vulnerability ID VCID-s8u8-xbdk-87dj
Aliases CVE-2021-33829
GHSA-rgx6-rjj4-c388
Summary 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.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (3)
CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
epss 0.49674 https://api.first.org/data/v1/epss?cve=CVE-2021-33829
cvssv3 6.1 https://ckeditor.com/blog/ckeditor-4.16.1-with-accessibility-enhancements/#improvements-for-comments-in-html-parser
cvssv3.1 6.1 https://ckeditor.com/blog/ckeditor-4.16.1-with-accessibility-enhancements/#improvements-for-comments-in-html-parser
generic_textual MODERATE https://ckeditor.com/blog/ckeditor-4.16.1-with-accessibility-enhancements/#improvements-for-comments-in-html-parser
cvssv3.1_qr MODERATE https://github.com/advisories/GHSA-rgx6-rjj4-c388
cvssv3.1 6.1 https://github.com/ckeditor/ckeditor4
generic_textual MODERATE https://github.com/ckeditor/ckeditor4
cvssv3.1 6.1 https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/core/CVE-2021-33829.yaml
generic_textual MODERATE https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/core/CVE-2021-33829.yaml
cvssv3.1 6.1 https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/drupal/CVE-2021-33829.yaml
generic_textual MODERATE https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/drupal/CVE-2021-33829.yaml
cvssv3.1 6.1 https://lists.debian.org/debian-lts-announce/2021/11/msg00007.html
generic_textual MODERATE https://lists.debian.org/debian-lts-announce/2021/11/msg00007.html
cvssv3.1 6.1 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NYA354LJP47KCVJMTUO77ZCX3ZK42G3T
generic_textual MODERATE https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NYA354LJP47KCVJMTUO77ZCX3ZK42G3T
cvssv3.1 6.1 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UVOYN2WKDPLKCNILIGEZM236ABQASLGW
generic_textual MODERATE https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UVOYN2WKDPLKCNILIGEZM236ABQASLGW
cvssv3.1 6.1 https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WAGNWHFIQAVCP537KFFS2A2GDG66J7XD
generic_textual MODERATE https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WAGNWHFIQAVCP537KFFS2A2GDG66J7XD
cvssv3.1 6.1 https://nvd.nist.gov/vuln/detail/CVE-2021-33829
generic_textual MODERATE https://nvd.nist.gov/vuln/detail/CVE-2021-33829
archlinux High https://security.archlinux.org/AVG-2069
cvssv3.1 6.1 https://www.drupal.org/sa-core-2021-003
generic_textual MODERATE https://www.drupal.org/sa-core-2021-003
cvssv3.1 6.1 https://www.npmjs.com/package/ckeditor4
generic_textual MODERATE https://www.npmjs.com/package/ckeditor4
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2021-33829
https://ckeditor.com/blog/ckeditor-4.16.1-with-accessibility-enhancements/#improvements-for-comments-in-html-parser
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-33829
https://github.com/ckeditor/ckeditor4
https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/core/CVE-2021-33829.yaml
https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/drupal/CVE-2021-33829.yaml
https://lists.debian.org/debian-lts-announce/2021/11/msg00007.html
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NYA354LJP47KCVJMTUO77ZCX3ZK42G3T
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NYA354LJP47KCVJMTUO77ZCX3ZK42G3T/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UVOYN2WKDPLKCNILIGEZM236ABQASLGW
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UVOYN2WKDPLKCNILIGEZM236ABQASLGW/
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WAGNWHFIQAVCP537KFFS2A2GDG66J7XD
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WAGNWHFIQAVCP537KFFS2A2GDG66J7XD/
https://nvd.nist.gov/vuln/detail/CVE-2021-33829
https://www.drupal.org/sa-core-2021-003
https://www.npmjs.com/package/ckeditor4
1015217 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1015217
ASA-202106-35 https://security.archlinux.org/ASA-202106-35
AVG-2069 https://security.archlinux.org/AVG-2069
GHSA-rgx6-rjj4-c388 https://github.com/advisories/GHSA-rgx6-rjj4-c388
USN-5340-1 https://usn.ubuntu.com/5340-1/
USN-USN-5340-2 https://usn.ubuntu.com/USN-5340-2/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://ckeditor.com/blog/ckeditor-4.16.1-with-accessibility-enhancements/#improvements-for-comments-in-html-parser
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://github.com/ckeditor/ckeditor4
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/core/CVE-2021-33829.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://github.com/FriendsOfPHP/security-advisories/blob/master/drupal/drupal/CVE-2021-33829.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://lists.debian.org/debian-lts-announce/2021/11/msg00007.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/NYA354LJP47KCVJMTUO77ZCX3ZK42G3T
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UVOYN2WKDPLKCNILIGEZM236ABQASLGW
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WAGNWHFIQAVCP537KFFS2A2GDG66J7XD
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2021-33829
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://www.drupal.org/sa-core-2021-003
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N Found at https://www.npmjs.com/package/ckeditor4
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.97782
EPSS Score 0.49674
Published At April 1, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-04-01T13:02:25.591259+00:00 GithubOSV Importer Import https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2021/06/GHSA-rgx6-rjj4-c388/GHSA-rgx6-rjj4-c388.json 38.0.0