Paige A Thompson – who also goes by the name “erratic” -was charged with a single count of computer fraud and abuse in the US district Court in Seattle.
Thompson made an initial appearance in court and was ordered to remain in custody pending a detention hearing on Thursday.
The hacker got information including credit scores and balances plus the social security numbers of about 140,000 customers, the bank said.
It will offer free credit monitoring services to those affected. The FBI raided Thompson’s residence and seized digital devices.
An initial search turned up files that referenced Capital One and “other entities that may have been targets of attempted or actual network intrusions”.
A public defender appointed to represent Thompson did not immediately return an email seeking comment.
Capital One, based in McLean, Virginia, said it found out about the vulnerability in its system on July 19 and immediately sought help from law enforcement to catch the perpetrator.
According to the FBI complaint, someone emailed the bank two days before that notifying it that leaked data had appeared on the web hosting site GitHub.
A month before that, the FBI said, a Twitter user who went by “erratic” sent Capital One direct messages warning about distributing the bank’s data, including names, birth dates and social security numbers.
“Ive basically strapped myself with a bomb vest, (expletive) dropping capitol ones dox and admitting it,” one said. “I wanna distribute those buckets i think first.”
Capital One said it believes it is unlikely the information was used for fraud, but it will continue to investigate.
The data breach affected about 100 million people in the US and 6 million in Canada.
Capital One Financial Corporation, the US’s seventh-largest commercial bank with $373.6 billion (£307 billion) in assets as of June 30, is the latest US company to suffer a major data breach in recent years.
In 2017, a data breach at Equifax, one of the major credit reporting companies, exposed the social security numbers and other sensitive information of roughly half of the US population.
Last week, Equifax agreed to pay at least $700 million to settle lawsuits over the breach in a settlement with federal authorities and states. The agreement includes up to $425 million in monetary relief to consumers.