glibc is vulnerable to an integer overflow when a malloc(>= 32 GiB) is increased via realloc() (and M_MMAP_THRESHOLD is set very large or mmap() based allocation is disabled entirely by setting M_MMAP_MAX=0). Only the first couple bytes of the buffer are copied, potentially leaving the majority of the returned buffer with unititialised memory instead of the original malloc()ed buffer's contents.  This may turn into a security problem if you rely on realloc() preserving the contents you wrote into the buffer after malloc().