Another question: What about Poland?
The Nazis don't really want to fight a two front war without having the majority of Western Europe contained because Hitler wouldn't have felt confident enough. Poland forms a natural border between Germany and Russia and if Socialist France existing, its more than likely that in the years leading up to the war, Germany has been influencing Poland, through friendship or threats. If Poland gave the Soviets military access, it would be a disaster to Hitler, but if the Poles wouldn't, it would mean that the Soviets would have three options:
1. Invade Poland: it would mean that Poles and Germans would technically be allies (similarly to how the Soviets and Allies were allies by circumstance against the Axis) and Germans and Italians could rush to the Polish border, more than likely resulting in a slog that would cause most of the collateral damage to Poland, a place that would serve as a supply line for the Soviets if they were to push into Germany. Worse, a totalitarian regime attacking a young republic would have probably been the last straw for the Allied Powers, as it was in our TL, meaning the Reds would be fighting against fascism and the British Empire.
2. Go around Poland: probably the worst option as it would result in pissing off the Allies and possibly getting them involved, as well as more enemies in the Balkans, possibly resulting the formation of a alliance solely from defending the Balkans from Red aggression or acceptance into the Allies. This means more enemies, sets up for future American involvement (although it's still incredibly unlikely), no help from France and usage of precious supplies, which the Reds can't waste, all without ever laying a foot on Nazi soil. Assuming that the Soviets somehow push around Poland, they have damaged infrastructure which can't transport supplies or troops, more land that they need to protect from possibly naval invasions meaning more supplies diverted from the Axis front, and insurgency groups that the British could now communicate with to aid in the further obstruction of supplies and troop movement, as well as possible assassination attempts, industrial sabotage and attacks on Soviet administration, espionage and war planning centers. Only possible benefit is the new officers gain the experience they so desperately need before facing the main threat.
3. Naval invasion to Ostpreussen, then Eastern German coast: least plausible idea as Soviets have a horrible navy and the Kriegsmarine would easily be able to repel any attempt to threaten Germany. This allows the Axis to focus on France and would probably lead to a breakthrough in the southern front on Italy after the Germans find that they can't breakthrough the Maginot or whatever socialist activist that it's named after now (because butterflies). France is eliminated and the Soviets find themselves with less supplies, less men, no allies and a stronger enemy.
In a TL where genocide is discovered, Poland would probably be guaranteed by the Allies to avoid further Nazi aggression, meaning that Poland is fully off-limits or else all the democrcies in the world will point a gun to your head, but this still means that Germany gets its barrier and the Soviets are forced to take 2 or 3. No matter what situation, Poland makes a war with Axis almost impossible without large Red losses.