Denial of service in CKEditor

Published: 2021-01-27

Risk	Low
Patch available	YES
Number of vulnerabilities	2
CVE-ID	CVE-2021-26271 CVE-2021-26272
CWE-ID	CWE-20
Exploitation vector	Network
Public exploit	N/A
Vulnerable software Subscribe	CKEditor Web applications / JS libraries
Vendor	CKSource

Security Bulletin

This security bulletin contains information about 2 vulnerabilities.

1) Input validation error

EUVDB-ID: #VU50055

Risk: Low

CVSSv3.1: 4.1 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:L/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-26271

CWE-ID: CWE-20 - Improper input validation

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a regular expression denial of service (ReDoS) attack.

The vulnerability exists due to insufficient validation of user-supplied input. A remote attacker can trick the victim to paste a specially crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin) and perform a regular expression denial of service (ReDoS) attack.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

CKEditor: 4.0.0 - 4.15.1

External links

http://github.com/ckeditor/ckeditor4/blob/major/CHANGES.md#ckeditor-416

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.

2) Input validation error

EUVDB-ID: #VU50054