Earnings were $5.6bn, a huge improvement from a $380m loss in the year-ago period due to heavy legal charges. Earnings were released on the Internet several hours ahead of the planned 11:00 GMT time.
The incident comes as the Federal Bureau of Investigations and other agencies investigate a huge hacking breach at JPMorgan, the largest US bank by assets.
JPMorgan has said hackers accessed information on about 76 million households and seven million businesses. But the bank has said there is no evidence of fraud resulting from the security breach.
A JPMorgan spokesperson said on Tuesday the early release "appears to have been a problem with Shareholder.com earlier this morning." Shareholder.com, a service that facilitates communication between companies and investors, was acquired by Nasdaq in 2006.
Earnings translated into $1.36 per share, two cents below expectations.
JPMorgan lost $380m in the year-ago period as it faced a battery of charges to settle lawsuits on its preparation of mortgage-backed securities ahead of the housing bust and a host of other controversies.
In the third quarter, revenues rose to $24.25bn from $23.12bn reported last year, slightly above the $24.01bn projected by analysts.
Shares of JPMorgan fell 0.6% to $57.82 in pre-market trade.