NULL Pointer Dereference
gdImageClone in gd.c in libgd 2.1.0-rc2 through 2.2.5 has a NULL pointer dereference allowing attackers to crash an application via a specific function call sequence. Only affects PHP when linked with an external libgd (not bundled).
CWE-476 - NULL Pointer Dereference
A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit.