He is expected to make a full recovery.
"Early this morning, an assailant broke into the Pelosi residence in San Francisco and violently assaulted Mr. Pelosi," spokesperson Drew Hammill wrote in a statement. "The assailiant is in custody and the motivation for the attack is under investigation. Mr. Pelosi was taken to the hospital where he is receiving excellent medical care and is expected to make a full recovery."
Pelosi herself was not in San Francisco at the time of the attack, Hammill said.
"The speaker and her family are grateful to the first responders and medical professionals involved, and request privacy at this time," he added.
As noted by Axios, the "alleged attack comes amid an uptick in threats against members of Congress and a series of security incidents over the summer."