A buffer overflow was addressed with improved size validation. This issue is fixed in iOS 13.4 and iPadOS 13.4, macOS Catalina 10.15.4, tvOS 13.4, watchOS 6.2, iTunes for Windows 12.10.5, iCloud for Windows 10.9.3, iCloud for Windows 7.18. Multiple issues in libxml2.
https://support.apple.com/HT211107
https://support.apple.com/HT211106
https://support.apple.com/HT211105
https://support.apple.com/HT211103
https://support.apple.com/HT211102