CVE-2020-27770

Due to a missing check for 0 value of `replace_extent`, it is possible for offset `p` to overflow in SubstituteString(), causing potential impact to application availability. This could be triggered by a crafted input file that is processed by ImageMagick. This flaw affects ImageMagick versions prior to 7.0.8-68.

Source: CVE-2020-27770