The vulnerability, as described, is a stack overflow in ImageMagick's fx operation due to a missing depth check. The analysis of the provided security advisory and the associated patch confirms this. By comparing the git tags for the patched version 7.1.2-23 and the preceding version 7.1.2-22, I identified the fixing commit 06fb1aa7589f4eec363b33c2bbda5986a92bb259. The patch modifies the file MagickCore/fx.c, specifically the function GetOperand. The changes introduce a recursion depth check using a counter pfx->teDepth. The function GetOperand is recursive, and without this check, a specially crafted expression could lead to excessive recursion, exhausting the stack and causing a denial of service. Therefore, GetOperand is the vulnerable function that would appear in a runtime profile during the exploitation of this vulnerability.