Issue summary: Applications using AES-CFB128 encryption or decryption on
systems with AVX-512 and VAES support can trigger an out-of-bounds read
of up to 15 bytes when processing partial cipher blocks.

Impact summary: This out-of-bounds read may trigger a crash which leads to
Denial of Service for an application if the input buffer ends at a memory
page boundary and the following page is unmapped. There is no information
disclosure as the over-read bytes are not written to output.

The vulnerable code path is only reached when processing partial blocks
(when a previous call left an incomplete block and the current call provides
fewer bytes than needed to complete it). Additionally, the input buffer
must be positioned at a page boundary with the following page unmapped.
CFB mode is not used in TLS/DTLS protocols, which use CBC, GCM, CCM, or
ChaCha20-Poly1305 instead.