Market Sell-off Extends the September Slide: China and the Evergrande Effect -- What Investors Should Do Now. Plus, Treasury Secretary Yellen’s Debt Ceiling Warning, Pfizer's New Data on COVID Vaccines for Kids, and U.S. Plans to Ease Travel Restrictions.

Squawk on the Street

Carl Quintanilla, Jim Cramer and David Faber kicked off the week with a breakdown of the market sell-off, sparked by worries about contagion from the problems of Chinese property giant Evergrande. The company has hundreds of billions in debt and risks defaulting on a payment this week. The anchors also looked at where this week's Fed meeting, Washington's haggling over the reconciliation bill and the debt ceiling fit into the market picture, with Treasury Secretary Janet Yellen saying in an op-ed that Congress' failure to raise the debt limit would result in "economic catastrophe." Cramer calls this a "faux perilous" moment, adding that everything could be contained by "responsible politicians." He also talks about the September slide and how investors should approach what has been historically a rough time of the year for stocks. Carl, Jim and David also discussed Pfizer and BioNTech's announcement of new data showing their COVID vaccine is safe and generates what they call a "robust" immune response in a clinical trial of kids ages 5 to11. The anchors reacted to Pfizer board member and former FDA commissioner Dr. Scott Gottlieb's comment to CNBC, in which he said a vaccine for kids could be available as early as late October 2021. Also in focus: The U.S. planning to ease travel restrictions for foreign nationals who are vaccinated against COVID, a look ahead to this week's earnings from companies including Nike, why cryptocurrencies are under pressure, and "SPAC-ulation" intensifies.