CVE-2021-26271
CKEditor 4 ReDoS Vulnerability
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
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
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
- Record
CVE-2021-26271- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:N/A:P - Weakness
- CWE-829
- Updated
- 2026-11-02
CVE List No score
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
- Record
CVE-2021-26271- Updated
- 2026-11-02
EUVDEUVD-2022-4431 No score
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
- Record
EUVD-2022-4431- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-jv4c-7jqq-m34x
CKEditor 4 ReDoS Vulnerability
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
- Record
GHSA-jv4c-7jqq-m34x- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-1333
- Updated
- 2026-11-02
OSV
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
- Record
CVE-2021-26271- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-26271
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
- Record
DEBIAN-CVE-2021-26271- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVGHSA-jv4c-7jqq-m34x
CKEditor 4 ReDoS Vulnerability
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
- Record
GHSA-jv4c-7jqq-m34x- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-1333
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-26271
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).
- Record
UBUNTU-CVE-2021-26271- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
ckeditor4-devnpm |
before 4.16 | 4.16 |
ckeditorDebian:12 |
before 4.16.0+dfsg-1 | 4.16.0+dfsg-1 |
ckeditorUbuntu:Pro:16.04:LTS |
All versions, plus listed versions 4.4.4+dfsg1-34.5.6+dfsg-14.5.7+dfsg-14.5.7+dfsg-24.5.7+dfsg-2ubuntu0.16.04.1~esm14.5.7+dfsg-2ubuntu0.16.04.1~esm24.5.7+dfsg-2ubuntu0.16.04.1~esm3 |
None known |
ckeditorUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 4.5.7+dfsg-24.5.7+dfsg-2ubuntu0.18.04.14.5.7+dfsg-2ubuntu0.18.04.1+esm14.5.7+dfsg-2ubuntu0.18.04.1+esm2 |
None known |
ckeditorUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 4.11.1+dfsg-14.12.1+dfsg-14.12.1+dfsg-1ubuntu0.14.12.1+dfsg-1ubuntu0.1+esm14.12.1+dfsg-1ubuntu0.1+esm2 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-26271 is a medium vulnerability (CVSS 6.5) in Ckeditor, published January 26, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.99%, the 80th percentile. Fixed in ckeditor4-dev 4.16.
References
github.com/ckeditor/ckeditor4/blob/major/CHANGES.md
oracle.com//security-alerts/cpujul2021.html
ckeditor.com/blog/CKEditor-4.16-with-improved-image-pasting-High-Contrast-support-and-a-new-color-API
nvd.nist.gov/vuln/detail/CVE-2021-26271
web.archive.org/web/20210128132707/https://ckeditor.com/blog/CKEditor-4.16-with-improved-image-pasting-High-Contrast-support-and-a-new-color-API