Mr Jack was a so-called "white hat" hacker who used his great skills to help companies improve their security.
Black Hat organisers said they would not replace Jack's session at the conference, saying the hour would be left vacant for to commemorate his life and work.
"Lost but never forgotten our beloved pirate, Barnaby Jack has passed.", said Mr Jack's most recent employer, the cybersecurity consulting firm IOActive Inc, said on Twitter, adding that Mr Jack was a "visionary" whose work had saved lives.
Even an arm of the US government paid tribute to Mr Jack for his work on medical devices.
"The work that Barnaby Jack and others have done to highlight some of these vulnerabilities has contributed importantly to progress in the field," said William Maisel, deputy director for science at the Food and Drug Administration's Center for Devices and Radiological Health.
"He was passionate about finding security bugs before the bad guys," added longtime security industry executive Stuart McClure, who gave Mr Jack one of his first jobs and also had worked with him at Intel Corp's McAfee, a computer security company.
"He was one of those people who was put on this earth to find vulnerabilities that can be exploited in a malicious way to hurt people," Mr McClure said.