The unnamed 29-year old suffered multiple, severe stab wounds to her head and body in what police described as an "extremely brutal" attack.
She was attacked yards from her home after getting off a bus in Krithia Road, Dagenham, at 21:40 GMT on Monday.
Police say they believe the attack was carried out by a stranger but are "keeping an open mind".
Passers-by attempted to help the woman, who remains in a critical condition in a hospital in east London.
Due to the nature of the attack investigators do not have a description of a suspect at this point and there have been no arrests.
Police appealed for two women who stopped to help the victim, or anyone else with information, to contact them.
DCI Gary Holmes, of Homicide and Major Crime Command, told BBC London: "This is a really brutal and horrific stabbing of a young lady coming home from work.
"That attack has left her in a terribly critical condition, currently in hospital in a life threatening condition and we are desperate to locate the person who committed... that attack."
A woman in east London has been left fighting for her life after an apparently random knife attack.