The Corona Borealis supercluster has been observed with the millimeter and infrared testa grigia observatory (MITO). Here we present the results of the observations together with a comparison with observations performed at 33 GHz with the very small array (VSA) interferometer. We have observed in the direction of the supercluster toward a cosmic microwave background (CMB) cold spot previously detected in a VSA temperature map. We claim a weak detection of a faint signal compatible with a SZ effect characterized at most by a comptonization parameter y=(7.8-4.4+5.3)×10 68% CL. The low level of confidence in the presence of a SZ signal invites us to study this sky region with higher sensitivity and angular resolution experiments such as already planned upgraded versions of VSA and MITO. This is the first millimetric evidence of unknown cluster/diffuse intra-supercluster gas (possibly warm hot intergalactic medium (WHIM)) interacting, via inverse Compton, scattering with the CMB.