An issue was discovered in Suricata 4.1.4. By sending multiple IPv4 packets that have invalid IPv4Options, the function IPV4OptValidateTimestamp in decode-ipv4.c tries to access a memory region that is not allocated. There is a check for o-len < 5 (corresponding to 2 bytes of header and 3 bytes of data).

Then, "flag = (o-data + 3)" places one beyond the 3 bytes, because the code should have been "flag = (o-data + 1)" instead.