Similar to issue #143 a very high value for colspan in <th> or <td> elements can cause resource exhaustion and denial of service on a server or a system freeze locally.

The code to reproduce:
md = markdownify('<table><tr><th colspan="999999999"></th></tr><table>')

If you check the HTML Living Standard the allowed values for colspan are 1 until 1000, so the processed values should be limited to this range.