nested lists `Maximum call stack size exceeded`

[UziTech]

I found another security issue trying to get nested lists to fail with a recursion error similar to #1462

const marked = require('marked');

const iterations = 300;
let spaces = 0;
let markdown = '';
for (let i = 0; i < iterations; i++) {
  markdown += ' '.repeat(spaces) + '- a\n';
  spaces += 2;
}

marked(markdown);

300 iterations takes about 3 seconds 600 iterations takes about 40 seconds

[UziTech]

commonmark.js has a similar issue https://github.com/commonmark/commonmark.js/issues/160

[andersk]

A more straightforward way to get a recursion error with nested lists is marked('- '.repeat(5000) + 'a').

[UziTech]

@andersk good call, looks like the DoS is in the number of characters. but we still have an issue with Maximum call stack size exceeded.

I'm not sure this one will be as easy to fix as blockquote since nested lists are not always the only thing in the list item.

We might just have to limit the number of nested lists.

[x13machine]

Looks like the list regex needs to be fixed or replaced with javascript.

[UziTech]

In this case, it isn't a problem with a regex. It is a problem with using recursion in the lexer. The solution would be to use regex and loop like in the block quote fix.

For now I think this is a case where failing is fine because it doesn't cause a redos attack and it is very unlikely someone would legitimately have 5000 nested lists.