We study the heat flow for Yang-Mills connections on R d × SO(d). It is wellknown that in dimensions 5 ≤ d ≤ 9 this model admits homothetically shrinking solitons, i.e., self-similar blowup solutions, with an explicit example given by Weinkove [35]. We prove the nonlinear asymptotic stability of the Weinkove solution under small equivariant perturbations and thus extend a result by the second author and Donninger for d = 5 to higher dimensions. At the same time, we provide a general framework for proving stability of self-similar blowup solutions to a large class of semilinear heat equations in arbitrary space dimension d ≥ 3, including a robust and simple method for solving the underlying spectral problems.