F5 Networks CEO Manny Rivelo, who took the position less than five months ago, resigned this weekend due to unspecified “personal conduct matters,” the company announced in an SEC filing on Monday. He will be replaced by former F5 CEO John McAdam while the company searches for a permanent replacement.

“I want to emphasize that these actions are in no way related to the Company’s operating performance or financial condition,” F5’s Lead Independent Director on the board Alan Higginson said in a statement. “This change in management, while unexpected, is strictly related to personal conduct matters. We are confident that F5 will be in good hands with John leading the Company forward.”

Rivelo, who replaced longtime CEO McAdam in July, first joined F5 in 2011, after 19 years with Cisco. He was in charge of the company’s strategic development, product management and global marketing strategy as Executive Vice President of Strategic Solutions before being named as McAdam’s successor back in April.

The SEC filing says his resignation was “not due to any disagreement with the Company on any matter relating to the Company’s operations, policies or practices.”

GeekWire has reached out to F5 for more details and will update this post when we hear more. McAdam was headed into retirement when he left the company after 15 years.

Update: A F5 spokesperson tells GeekWire McAdam will only serve as interim CEO “during this time of need.”

F5 stock is up 1.74 percent in after-hours trading, at $97.99/share.

This is a developing story and will be updated as more information becomes available.

Here is the text of the news release issued by the company today.