CommuniCrypt Mail versions up to and including 1.16 contains a stack-based buffer overflow vulnerability in its ANSMTP.dll and AOSMTP.dll ActiveX controls, specifically within the AddAttachments() method. This method fails to properly validate the length of input strings, allowing data to exceed the bounds of a fixed-size stack buffer. When invoked with an overly long string, the control can corrupt adjacent memory structures, including exception handlers, leading to potential control flow disruption.