GJ 367b is a hot, airless sub-Earth with an equilibrium temperature of 1370 K and a density of 10.2 ± 1.3 g/cm³. Observations using the James Webb Space Telescope (JWST) reveal no detectable atmosphere, no heat redistribution, and a low albedo (A_B ≈ 0.1). The planet's emission spectrum is consistent with a blackbody with no heat redistribution, ruling out atmospheres of 1 bar or more for many compositions. The lack of heat redistribution implies that 1 bar atmospheres are ruled out for a wide range of compositions, while 0.1 bar atmospheres are consistent with the data. The planet's surface is likely molten, suggesting it has lost most of its initial volatile inventory. The observations indicate that GJ 367b is far above the "cosmic shoreline," making the absence of an atmosphere unsurprising. The study highlights the importance of JWST in characterizing exoplanets, particularly M dwarf planets, and underscores the need for further observations of planets closer to or below the cosmic shoreline to understand atmospheric presence. The findings contribute to the understanding of planetary formation and atmospheric evolution, particularly for small rocky planets orbiting M dwarfs.GJ 367b is a hot, airless sub-Earth with an equilibrium temperature of 1370 K and a density of 10.2 ± 1.3 g/cm³. Observations using the James Webb Space Telescope (JWST) reveal no detectable atmosphere, no heat redistribution, and a low albedo (A_B ≈ 0.1). The planet's emission spectrum is consistent with a blackbody with no heat redistribution, ruling out atmospheres of 1 bar or more for many compositions. The lack of heat redistribution implies that 1 bar atmospheres are ruled out for a wide range of compositions, while 0.1 bar atmospheres are consistent with the data. The planet's surface is likely molten, suggesting it has lost most of its initial volatile inventory. The observations indicate that GJ 367b is far above the "cosmic shoreline," making the absence of an atmosphere unsurprising. The study highlights the importance of JWST in characterizing exoplanets, particularly M dwarf planets, and underscores the need for further observations of planets closer to or below the cosmic shoreline to understand atmospheric presence. The findings contribute to the understanding of planetary formation and atmospheric evolution, particularly for small rocky planets orbiting M dwarfs.