At about 1am on Sunday, the victim, a woman in her 40s who needs crutches to walk, was walking along Wheelgate in Malton.
She was approached from behind and with no obvious motive was punched once in the face, causing her to stumble to the ground.
As a result, she suffered chipped teeth and cut and swollen lips and was taken to hospital by ambulance.
Police are appealing for any information that may help to identify the offender.
Call 101, select option 2 and ask for PC Paul Fenwick or Malton Police, or email [email protected]
Alternatively, call Crimestoppers anonymously on 0800 555 111.