It is impossible to say with only the information given. It would probably be difficult, however, but more for low marks that the other facts.
The candidate needs to show, in application materials, a high probability of success. Nothing you state makes that success obvious. But letters of recommendation are also important and there can be reasons for low grades that aren't so much related to ability in mathematics. Even extreme focus on a research topic could cause poor performance elsewhere.
A committee would need to consider the entire package. The competition is also fierce and many in the pool won't have the same negative aspects.
It might be marginally easier to do this in the US than in EU as the doctoral education process can be longer and have more room to make up deficits.
But it isn't promising as stated.