All three major U.S. indexes ended Thursday in the red, bogged down by a further pullback in Oracle, as well as a jump in rates.

The S&P 500 closed down 0.50% at 6,604.72, as did the Nasdaq Composite, which settled at 22,384.70. The Dow Jones Industrial Average shed 173.96 points, or 0.38%, to finish at 45,947.32.

Oracle slid 5%, putting the stock on track to post a third straight day of losses, as questions over the state of the artificial intelligence trade lingered. The market action appears to be reflecting concerns about record-high valuations and potentially risky circular relationships in the AI industry after some recent deals.

Through Thursday's close, Oracle, which led the latest leg of the bull market, is off nearly 16% from its recent high. Thursday's decline was partly driven by a sell rating issued in new coverage by Rothschild & Co. Redburn, which predicted a 40% pullback because the "market materially overestimates" how much Oracle's recent AI deals will boost the company's core cloud business.

"Oracle had just a massive run-up. Some giveback and softness is probably warranted with how quickly and how dramatically the market cap has exploded," said Keith Buchanan, senior portfolio manager at Globalt Investments. He also cited "some skepticism" pertaining to the company's explosive cloud infrastructure growth projections that it reported earlier this month.

"The magnitude of those orders is eye-catching, but if it's concentrated into very few orders from very few end markets, then of course there's a risk," he told CNBC.

Alongside Oracle, Tesla was among the day's laggards, falling 4%.

A jump in yields added to the selling in tech shares, causing investors to take off some risk. The 10-year Treasury yield touched 4.2% after data on initial claims for unemployment insurance came in lower than expected.

First-time filings for jobless benefits were at a seasonally adjusted 218,000 for the week ended Sept. 20, the Labor Department said Thursday. That's below the 235,000 that economists polled by Dow Jones had estimated and 14,000 less than the previous period's revised initial unemployment claims, which had also eased after seeing a brief spike the week before that.

The solid jobs data, as well as a strong upward revision in second-quarter gross domestic product to 3.8%, could mean the Federal Reserve hesitates before cutting rates again, undermining a key catalyst for the bulls.

Investors are also cautious ahead of the personal consumption expenditures price index due Friday and are monitoring developments regarding a potential government shutdown. If the government were to shut down, that could mean mass firings in the federal government, as the Office of Management and Budget has said in a memo that agencies should prepare "reduction in force" plans, according to NBC News.