import msgpack

unpacker = msgpack.Unpacker()
unpacker.feed(b"\x91")

try:
    unpacker.skip()
except msgpack.OutOfData:
    pass

unpacker.feed(b"\x00")
unpacker.unpack()

$ python reproducer.py
Segmentation fault (core dumped)

import msgpack

# Incomplete skip() followed by skip()
skip_again = msgpack.Unpacker()
skip_again.feed(b"\x91")

try:
    skip_again.skip()
except msgpack.OutOfData:
    pass

skip_again.feed(b"\x00")
assert skip_again.skip() is None

# Incomplete unpack() followed by unpack()
unpack_again = msgpack.Unpacker()
unpack_again.feed(b"\x91")

try:
    unpack_again.unpack()
except msgpack.OutOfData:
    pass

unpack_again.feed(b"\x00")
assert unpack_again.unpack() == [0]