According to the U.S. Chamber of Commerce, 61.6 million Americans are employed by small businesses — nearly half of the U.S. workforce.

However, a study released Tuesday by online financing platform Stenn shows that almost a quarter of those businesses are on precarious financial ground.

Over one in five small and medium-sized businesses (SMBs), or, those with at least one and at most 500 employees, said they only have one to five months of cash reserves on hand for emergencies.

That means, according to the study, one in five U.S. SMBs could run out of cash by Christmas and are especially “vulnerable to financial shocks.”

The study noted that 50% of SMBs fail in their first year and 45% fail within the first five years, and also that these businesses are essential: They are the nation’s biggest employer by category.

Related: We Asked 500 Small Business Owners What They Thought About the Economy, Inflation and the Upcoming Election. Here Are the Results.

“Small businesses are the unsung heroes of the economy in the U.S.,” Stenn chief commercial officer Noel Hillman stated.

In good news, most SMBs have more cash on hand — more than half (56.4%) or close to three in five SMBs said they had six to 18 months of cash reserves.

Also, over four in five businesses said they were months away from scaling their businesses and increasing revenue. Around 45% said scaling would take six to 18 months, while 36.8% said it would take just one to five months.

The survey was based on a sample of 250 founders, owners, and CEOs who lead businesses with at least $2.5 million in annual revenue with one to 500 employees. It was conducted between August 29 and September 5.

Related: A Small Business Owner’s Guide to Managing Funds and Investments