Hertz stock jumped in premarket trading Thursday after the company's quarterly earnings topped Wall Street estimates, offering some relief to weary investors.

The car rental company Thursday announced a second-quarter per-share loss of 11 cents from sales of $2.4 billion. Wall Street was looking for a loss of 24 cents a share from sales of just under $2.3 billion, according to FactSet. A year ago, Hertz reported a comparable 29-cent loss from sales of just under $2.2 billion.

Shares were up 17% at $1.82 in premarket trading, while S&P 500 and Dow Jones Industrial Average futures were up 0.1% and 0.2%, respectively.

Revenue per rental unit rose 8% year over year. "This quarter's results reflect the disciplined execution of our strategy and our consistent commercial strength," said CEO Gil West in a news release. "Our performance demonstrates the progress we're making in transforming the business and delivering tangible operational improvements across the company."

The results are a relief after a tough year for the company. They could be a problem for short sellers. Almost 30% of Hertz stock available to trade has been borrowed and sold short by bearish investors, betting on price declines. That's a very high short interest, roughly 10 times the average stock.

But high short interest always brings the risk of a short squeeze, when some good news sends bears rushing to buy stock, covering their bearish bets, a process which can send any stock up higher than expected.

To be sure, short sellers got the recent direction correct. Coming into Thursday, Hertz stock this year has declined 70%. Earnings estimates have gone from a per-share loss of roughly 50 cents to a per-share loss of about $1 over the past few months.

Shares dropped 41% on June 24 after the company said weakness in the used car market would hit second-quarter earnings. Rental car companies buy and sell many vehicles, making resale values an important metric to track.

Things turned out better than expected, though. Hertz generated second-quarter earnings before interest, taxes, depreciation, and amortization of $81 million, at the high end of the company's prior guidance range.

Investors can expect a positive stock price reaction to second-quarter numbers. Just how positive is hard to say.