Magma remobilization is the process by which magma is reactivated and mobilized within a mush system. A mush system is a partially molten mixture of a solid crystalline matrix and interstitial liquid, typically involving the solidification of a magmatic system. Magma remobilization can occur in a variety of ways, including the injection of new magma into an existing system due, for example, to the upward migration of hot, buoyant magma from deeper levels or the mechanical deformation of the solid matrix that allows previously trapped interstitial liquid to become mobile. Another mechanism may involve volatile fluxing, mainly CO2 exsolved from larger depths. In a mush system, the process of magma remobilization can lead to changes in the system's crystal content and texture, as well as changes in the chemical composition of the magma. Overall, understanding the processes involved in magma remobilization in mush systems can shed light on the complex dynamics of magmatic systems and their associated hazards. Here, I show under which thermodynamic and chemical constraints CO2-fluxing may promote the remobilization of shallow magma batches, such that volcanic hazard may be extremely high because it is associated with the remobilization of apparently inactive magma batches. In contexts where discharged fluids come essentially from deep magma reservoirs, the possibility of rapid and abrupt remobilization of shallow magma batches in a mush system cannot absolutely be discarded, even if such shallow batches do not appear to be involved in melt-fluid exchanges and are then ruled out as possible sources of the fluid either discharged at surface or infiltrating hydrothermal systems. The implications of rapid shallow magma remobilization are then discussed with reference to Campi Flegrei, where the active source of magmatic fluids is shown by many research groups to be at least 8 km deep. Any scenario considering that the eruptive magma is the deep magma sourcing CO2-rich fluids upward may seriously underestimate the volcanic hazard, independent of any consideration about magma ascent times.