I have a question in mind. Suppose we have a collision-resistant unkeyed-hash function $H(·)$ which outputs a 128-bit digest, and a semantic secure symmetric encryption $E(·,·)$ in the following way, we can design a Message Authentication Code (MAC) in this manner, so given a message $m$ and the secret key $k$, the mac is the encrypted digest, $t=E(k, H(m))$.
Is it susceptible to forgery if the encryption is in CBC mode or CTR mode? My intuition tells me that it is possible, but I have no idea of constructing the forgery for them. Any suggestion is welcome, thanks!