The ruling means Fenati will be forced to skip the Aragon round in two weeks' time as well as the championship's first visit to Thailand early next month.
It is understood that the Marinelli Snipers team will not appeal the decision.
San Marino Grand Prix
Dovizioso takes Misano win, Lorenzo crashes
09/09/2018 AT 13:41
Fenati was disqualified from the Misano race for "irresponsible riding" after leaning across and grabbing Manzi's brake lever on the back straight heading towards the Turn 8 left-hander while battling over 17th place.
A stewards' bulletin read: "Fenati [was] found to have deliberately attempted to cause danger to another rider [Manzi] by interfering with his machine whilst on track.
"This contravenes Article 1.21.2 of the FIM World Championship Grand Prix Regulations [which states] "Riders must ride in a responsible manner which does not cause danger to other competitors or participants, either on the track or in the pitlane.
"It is therefore an infringement of the FIM World Championship Grand Prix Regulations. This is considered a serious offense."
Forward Racing's Manzi crashed out of the race shortly after the incident.
Fenati holds 19th position in this year's championship, having stepped up to the secondary category after finishing runner-up in Moto3 last season.
San Marino Grand Prix
Lorenzo sets new lap record for pole
08/09/2018 AT 13:51
Grand Prix Valencia
'An inspiration for me' - Federer leads Rossi tributes after final race
14/11/2021 AT 17:23