<p><it>Abstract</it>—In this brief contribution, we derive an exact expression for $<tmath>(n - 1)</tmath>$-cube reliability in an $<tmath>n</tmath>$-cube using a new probability fault model and an existing random fault model. Approximate results are also obtained for $<tmath>m</tmath>$-cube reliability for values of $<tmath>m</tmath>$ smaller than $<tmath>n - 1.</tmath>$ We show that the proposed probability model for computing subcube reliability is equally accurate, but computationally more efficient than the existing random fault model.</p>