CVE-2021-3696

A heap out-of-bounds write may heppen during the handling of Huffman tables
in the PNG reader. This may lead to data corruption in the heap space.
Confidentiality, Integrity and Availablity impact may be considered Low as
it’s very complex to an attacker control the encoding and positioning of
corrupted Huffman entries to achieve results such as arbitrary code
execution and/or secure boot circumvention. This flaw affects grub2
versions prior grub-2.12.