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Vulnerability record · CVE-2021-26271 · published 26 January 2021

CVE-2021-26271: Ckeditor inclusion from untrusted sphere vulnerability

Ckeditor · Ckeditor

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).

6.5 CVSS 3.1 Medium EPSS 2.0% · top 20.4% CWE-829 · Inclusion from untrusted sphere
6.5CVSS 3.1 base score, v2 4.3
2.0%EPSS exploitation probability, 30 days
NoNot in CISA KEV
7Affected product versions listed by NVD
8References
25 Aug 2026Last modified by NVD

Description

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).

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

Affected products

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

References

LinkTags
https://ckeditor.com/blog/CKEditor-4.16-with-improved-image-pasting-High-Contrast-support-and-a-new-color-API/#security- Vendor Advisory
https://github.com/ckeditor/ckeditor4/blob/major/CHANGES.md#ckeditor-416 Release NotesThird Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html PatchThird Party Advisory
https://ckeditor.com/blog/CKEditor-4.16-with-improved-image-pasting-High-Contrast-support-and-a-new-color-API/#security- Vendor Advisory
https://github.com/ckeditor/ckeditor4/blob/major/CHANGES.md#ckeditor-416 Release NotesThird Party Advisory
https://www.oracle.com//security-alerts/cpujul2021.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpuoct2021.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-26271), CISA KEV, FIRST EPSS (scores of 2026-09-28). This page is refreshed as NVD updates the record.