Impact

What kind of vulnerability is it?

Denial of service.

The regular expression inline.reflinkSearch may cause catastrophic backtracking against some strings.
PoC is the following.

import * as marked from 'marked';

console.log(marked.parse(`[x]: x

\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](\\[\\](`));

Who is impacted?

Anyone who runs untrusted markdown through marked and does not use a worker with a time limit.

Patches

Has the problem been patched?

Yes

What versions should users upgrade to?

4.0.10

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

Do not run untrusted markdown through marked or run marked on a worker thread and set a reasonable time limit to prevent draining resources.

References

Are there any links users can visit to find out more?

• https://marked.js.org/using_advanced#workers
• https://owasp.org/www-community/attacks/Regular_expression_Denial_of_Service_-_ReDoS

For more information

If you have any questions or comments about this advisory:

• Open an issue in marked