PyMuPDF 1.25.3 before 2.0 contains a stack-based buffer overflow vulnerability in JM_set_annot_callout_line() that copies a caller-supplied number of callout points into a fixed three-element stack array. Attackers who control the callout argument passed to Page.add_freetext_annot() can supply four or more points to overwrite the stack frame, crashing the process or executing code.