Root Cause Analysis: Looking at the given vulnerable code line and its context, the CWE-787 (out-of-bounds write) vulnerability exists in the code because the variable `cc->tfms_count` is used to allocate memory for the `cc->tfms` array without checking if `cc->tfms_count` is 0. If `cc->tfms_count` is 0, then allocating memory for `cc->tfms` with `cc->tfms_count * sizeof(crypto_skcipher *)` will result in an out-of-bounds write vulnerability, which is CWE-787.