What could threaten a continued sharp rise in European share prices?

The rapid rise in European share prices in the first half of 2021 has some investors fearing a downward correction in European indices. What threats could lead to such a setback and prevent the euro-zone stock market indices from continuing to rise? Not an overvaluation of European equities, nor an equity market bubble in Europe, given the still very high level of the equity risk premium in Europe; Not a rise in long-term interest rates linked to the emergence of sustained, non-transitory inflation in the United States and Europe: current inflation is clearly transitory; Probably not, given the latest information, a new wave of COVID causing another downturn in activity; on the contrary, strong growth is expected in Europe; Then only "exogenous risks" remain : geopolitical or political crises, etc.