# CVE-2021-26272: CKEditor 4 ReDoS in Autolink plugin

Source: https://junglewise.ai/threats/cve-2021-26272-ckeditor-4-redos-in-autolink-plugin  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-10-13. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2021-26272 · Severity: low · CVSS 3.1 · Published 2021-10-13

CKEditor 4 is a widely-used rich text editor component embedded in web applications. A regular expression denial-of-service (ReDoS) vulnerability in its Autolink plugin can be triggered when a user pastes specially crafted URL-like text and presses Enter or Space, causing the editor to hang or become unresponsive and degrading application availability.

Technologies: [CKEditor 4](https://junglewise.ai/threats/technologies/ckeditor-4), [ckeditor4 (npm)](https://junglewise.ai/threats/technologies/ckeditor4). Vendors: [CKEditor](https://junglewise.ai/threats/vendors/ckeditor), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is CVE-2021-26272 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-26272 being exploited in the wild.

**How severe is CVE-2021-26272?** Low severity, with a CVSS score of 3.1, published 13 October 2021.

**Which products and versions are affected?** CKEditor 4 before 4.16.0; ckeditor4 (npm) SEMVER:introduced=0,fixed=4.16.0.

**Is there a fix for CVE-2021-26272?** Yes. ckeditor4 (npm): upgrade to 4.16.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2021-26272 attacked?** It is attacked over the network.

**Am I affected by CVE-2021-26272?** Check whether you run CKEditor 4 or ckeditor4 (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- ckeditor4 (npm): upgrade to 4.16.0 or later

  ```sh
  npm install ckeditor4@4.16.0
  ```


## Technical details

This vulnerability is a Regular Expression Denial of Service (ReDoS) attack vector in CKEditor 4 versions before 4.16.0, classified as CWE-829 (Inclusion of Functionality from Untrusted Control Sphere). The Autolink plugin contains a vulnerable regular expression that processes URL-like patterns when users press Enter or Space after pasting text. An attacker can craft malicious URL-like strings that cause catastrophic backtracking in the regex engine, consuming excessive CPU and causing the editor to hang. The attack requires user interaction (pasting and key press) but no authentication. The vulnerability was patched in CKEditor 4.16.0.

## Affected products

- CKEditor CKEditor 4 before 4.16.0

## Identifiers

- CVE-2021-26272
- GHSA-wpvm-wqr4-p7cw

## Timeline

- 2021-01-26: disclosed: NVD published
- 2021-10-13: advisory: GHSA advisory published
- 2021-10-15: patched: Fixed in CKEditor 4.16.0

## References

- [https://ckeditor.com/blog/CKEditor-4.16-with-improved-image-pasting-High-Contrast-support-and-a-new-color-API/](https://ckeditor.com/blog/CKEditor-4.16-with-improved-image-pasting-High-Contrast-support-and-a-new-color-API/)

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