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GHSA-hgmg-hhc8-g5wr

MediumCVSS 6.5 / 10
Published Jan 29, 2021·Last modified Mar 13, 2026
Affected Components(0)

No affected components available

Description

Impact

A regular expression denial of service (ReDoS) vulnerability has been discovered in the CKEditor 5 Markdown plugin code. The vulnerability allowed to abuse a link recognition regular expression, which could cause a significant performance drop resulting in a browser tab freeze. It affects all users using the CKEditor 5 Markdown plugin at version <= 24.0.0.

Patches

The problem has been recognized and patched. The fix will be available in version 25.0.0.

Workarounds

The user can work around the issue by:

  • Upgrading CKEditor 5 to version 25.0.0.
  • Disabling the Markdown plugin.

More information

If you have any questions or comments about this advisory:

Acknowledgements

The CKEditor 5 team would like to thank Erik Krogh Kristensen from the GitHub team for recognizing this vulnerability and Alvaro Muñoz from GitHub for reporting it.

Risk Scores
Base Score
6.5

The vulnerability can be exploited over the network without needing physical access. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the availability of the system.

Threat Intelligence
6.0

Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.

EPSS
1.79%

The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.

Exploit
Not available

We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.

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