An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 13.5 and iPadOS 13.5, macOS Catalina 10.15.5, tvOS 13.4.5, watchOS 6.2.5. Opening a maliciously crafted PDF file may lead to an unexpected application termination or arbitrary code execution.
https://support.apple.com/HT211175
https://support.apple.com/HT211171