Avaya president and CEO Lou D'Ambrosio has stepped down for medical reasons, an IDG News report said.
The IDG report also said Avaya's brief statement didn't elaborate on those medical reasons. D'Ambrosio had led the company for about two years.
Charles Giancarlo, a former high-level executive of Avaya rival Cisco Systems, will run the company full time while Avaya searches for a permanent replacement, the report said.
Giancarlo left Cisco earlier this year to become a managing director at Silver Lake Partners, a Silicon Valley investment company that took Avaya private last year along with Texas Pacific Group.
D'Ambrosio has also left the company's board but will remain in an advisory role.
Avaya has hired executive search firm Heidrick & Struggles to help Avaya find a replacement for D'Ambrosio.
Dave Roux, cofounder of Silver Lake, is the nonexecutive chairman of Avaya.