A Greater Anglia train travelled for 23 minutes with one of its doors open, according to accident investigators.
The door was finally closed when a passenger on the August 22 train travelling from London Liverpool Street to Southend Victoria alerted the driver.
The Rail Accident Investigation Branch (RAIB) said the train travelled at speeds of up to 80mph during the incident.
It said it will publish a document within weeks notifying rail operators what safety lessons can be learnt.
Greater Anglia spokesman, Martin Moran, said no one was injured and “there have been no further incidents since”.
“Safety is our highest priority. We immediately took the train out of service when this happened and carried out our own investigation into the incident,” he said.
“We have also carried out checks on every single door on that type of train that we have.”
A separate RAIB report in July found a Tube driver’s lack of sleep and food may have contributed to 10 doorways being left open during a journey between Finchley Road and West Hampstead.
The train travelled at nearly 40mph during the 56-second journey in September last year. No one was injured in the incident.
In response, the RAIB made four recommendations to London Underground that included improvements to door control systems, better training for drivers and raising awareness of the risks of fatigue.