git log has the ability to display commits using an arbitrary
format with its --format specifiers. This functionality is also
exposed to git archive via the export-subst gitattribute.
When processing the padding operators (e.g., %<(, %<|(,
%>(, %>>(, or %><( ), an integer overflow can occur in
pretty.c::format_and_pad_commit() where a size_t is improperly
stored as an int, and then added as an offset to a subsequent
memcpy() call.
This overflow can be triggered directly by a user running a
command which invokes the commit formatting machinery (e.g., git
log --format=...). It may also be triggered indirectly through
git archive via the export-subst mechanism, which expands format
specifiers inside of files within the repository during a git
archive.
This integer overflow can result in arbitrary heap writes, which
may result in remote code execution.