A gas turbine engine, comprising: a high-pressure compressor; and a mid-turbine frame, comprising: a vane extending from one end to another end along an axis; a first fitting; a second fitting spaced apart from the first fitting along the axis; a tube assembly located within the vane such that a cavity is defined between the vane and the tube assembly, the tube assembly comprising: an outer tube coupled to the first fitting and extending from the first fitting to the second fitting; an inner tube located within the outer tube and extending from the first fitting to the second fitting; and an outer passage defined between the outer tube and the inner tube, and an inner passage defined within the inner tube, wherein the cavity, the outer passage and the inner passage are fluidly isolated from one another, wherein the cavity is configured to direct a cooling flow at a first pressure and a first temperature through the cavity, the outer tube is configured to direct a buffer flow at the first pressure and a second temperature that is lower than the first temperature through the outer tube, and the inner tube is configured to direct a lubricant flow through the inner tube, wherein the cooling flow and the buffer flow are both bled from a same stage of the high-pressure compressor. a high-pressure compressor; and a mid-turbine frame, comprising: a vane extending from one end to another end along an axis; a first fitting; a second fitting spaced apart from the first fitting along the axis; a tube assembly located within the vane such that a cavity is defined between the vane and the tube assembly, the tube assembly comprising: an outer tube coupled to the first fitting and extending from the first fitting to the second fitting; an inner tube located within the outer tube and extending from the first fitting to the second fitting; and an outer passage defined between the outer tube and the inner tube, and an inner passage defined within the inner tube, wherein the cavity, the outer passage and the inner passage are fluidly isolated from one another, wherein the cavity is configured to direct a cooling flow at a first pressure and a first temperature through the cavity, the outer tube is configured to direct a buffer flow at the first pressure and a second temperature that is lower than the first temperature through the outer tube, and the inner tube is configured to direct a lubricant flow through the inner tube, wherein the cooling flow and the buffer flow are both bled from a same stage of the high-pressure compressor. a vane extending from one end to another end along an axis; a first fitting; a second fitting spaced apart from the first fitting along the axis; a tube assembly located within the vane such that a cavity is defined between the vane and the tube assembly, the tube assembly comprising: an outer tube coupled to the first fitting and extending from the first fitting to the second fitting; an inner tube located within the outer tube and extending from the first fitting to the second fitting; and an outer passage defined between the outer tube and the inner tube, and an inner passage defined within the inner tube, wherein the cavity, the outer passage and the inner passage are fluidly isolated from one another, wherein an outer tube coupled to the first fitting and extending from the first fitting to the second fitting; an inner tube located within the outer tube and extending from the first fitting to the second fitting; and an outer passage defined between the outer tube and the inner tube, and an inner passage defined within the inner tube, wherein the cavity, the outer passage and the inner passage are fluidly isolated from one another, wherein the cavity is configured to direct a cooling flow at a first pressure and a first temperature through the cavity, the outer tube is configured to direct a buffer flow at the first pressure and a second temperature that is lower than the first temperature through the outer tube, and the inner tube is configured to direct a lubricant flow through the inner tube, wherein the cooling flow and the buffer flow are both bled from a same stage of the high-pressure compressor.