A 54-year-old woman was scratched on the face after she was attacked while walking her dog.
The assault happened at around 11pm on Saturday night, when the dog walker was approached by a man in Meadowcroft Park, Aylesbury.
The man spoke to the victim before attacking her and running off, leaving her with a scratch to her left cheek and a minor injury to her stomach.
He is white, between 5ft 7ins to 5ft 10ins tall, with shaggy long hair. He was wearing dark clothing.
Police are appealing for any witnesses to call Det Con 5667 Lynda Stearman on the non-emergency number 101.
Alternatively they can call Crimestoppers anonymously on 0800 555 111, or visit www.crimestoppers-uk.org. No personal details are taken, information is not traced or recorded and you will not go to court.