Its possible that the Soviet cavalry depicted are those such as Budyonny's First Cavalry Army, which was a major cavalry formation that did at times engage with enemy forces using sabers. There was a famous battle during the Soviet-Polish Civil War, the Battle of Komrarow, where Polish Uhlans (cavalry after the French model) and elements of the First Cavalry Army engaged in melee combat as cavalry and not mounted infantry.

Cavalry charges with the sabre by Soviet cavalry would have been so rare as to be nearly unheard of in the Second World War. Standard infantry and combined arms tactics were used by Soviet cavalrymen in WWII once in contact with the enemy. The horses were mostly used on the march. Soviet Cavalry formations included a high proportion of support weapons like machine guns, mortars and artillery, (all horse drawn) so they would be competitive with infantry formations in firepower. Soviet cavalry often worked closely with armored units, and the infantrymen riding on tanks during Soviet attacks were often drawn from cavalry units.

I can't find a specific source for that picture, but I highly doubt it was taken in combat. The formation is too tight to be realistic even for a 19th century charge, even then, some dispersion was used to give the men room to maneuver their horses and use their weapons. Also the cameraman is slightly ahead of the charge. More likely a training or propaganda photo (cavalry charges are photogenic in any era!), or something completely anachronistic like a still from a movie.

While this isn't specifically about Soviet cavalry in the Second World War, there actually is quite a lot of information about cavalry charges against modern weaponry from the First World War. Many of these applications, as you would expect, failed. But, surprisingly, many also succeeded.

It seems that the defining factors of a successful cavalry charge in the modern era are basically a combination of three things.

One, that the terrain is suitable. Charging into mud or forest has always been a disaster, even when cavalry was the dominant arm of European warfare.

Two, that the firepower advantage is not overwhelming. In the First World War the small arms technology was not reasonably far behind that in the Second, with the exception of the proliferation of lighter machineguns and sub-machineguns. Attacking an enemy whose firepower has been depleted (for instance, lacking in automatic weapons or ammunition) is entirely possible.

Three, it helps a lot if the enemy is not very disciplined. They'll be scared by the charging horses and the thought of a sword through their face rather than keeping sense about them and just shooting calmly and accurately. So, green troops, or routing troops, are considerably more susceptible.

These three factors historically came together in the UK and allies' campaign in the Middle East in the First World War, where the open terrain and relatively unprepared and unsupplied Ottoman foes were commonly too ill-trained and ill-equipped to resist cavalry charges under favorable battlefield conditions. While accessing academic articles is as frustrating as ever, if you have the permissions for it this one is an interesting read on the subject.

In contrast, these three factors were routinely absent on the much more famous Western Front of WWI - it was extremely firepower dense due to its relatively short length and large amounts of troops and advanced modern weaponry, often muddy or forested, and commonly full of veteran soldiers - initially highly motivated. Under these conditions, all fairly obsolescent tactics were quickly put out to pasture: as many people died in the first few months of the war as in the next few years, cavalry included.

These same principles apply to the modern day battlefield as well, as the rare but nonetheless successful bayonet charges can still attest from deployments in Iraq and Afghanistan.

Assuming Soviet cavalry in fact did charge home with sabers, they could have certainly done so under these sorts of conditions. Keep in mind that the Germans were not the only ones fighting the Soviets on the Eastern Front - the lesser Axis members were there as well, such as Hungary or Romania. Charging routing Axis auxiliaries across favorable terrain would certainly still have been effective, albeit rare.

Is that a WW2 picture? During the Russian Revolution, both the Reds and the Whites used cavalry to a heavy extent, but during WW2, cavarly was only used in a support role, mostly in short raids in difficult terrain.