Because kernel needs to parse the data in some way and that parser apparently was broken enough. Whether it could be done in a more resilient manner, I don't kn

Because kernel needs to parse the data in some way and that parser apparently was broken enough. Whether it could be done in a more resilient manner, I don't know, you need to remember that antivirus works in hostile environment and can't necessarily trust userspace, so probably they need to verify signatures and parse payload in the kernel space.