An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in iOS 13.6 and iPadOS 13.6, macOS Catalina 10.15.6, tvOS 13.4.8, watchOS 6.2.8, iTunes 12.10.8 for Windows, iCloud for Windows 11.3, iCloud for Windows 7.20. Opening a maliciously crafted PDF file may lead to an unexpected application termination or arbitrary code execution.
https://support.apple.com/kb/HT211952
https://support.apple.com/kb/HT211935
https://support.apple.com/kb/HT211931
https://support.apple.com/kb/HT211850
https://support.apple.com/kb/HT211844
https://support.apple.com/kb/HT211843
https://support.apple.com/kb/HT211295
https://support.apple.com/kb/HT211294
https://support.apple.com/kb/HT211293
https://support.apple.com/kb/HT211291
https://support.apple.com/kb/HT211290
https://support.apple.com/kb/HT211289
https://support.apple.com/kb/HT211288
http://seclists.org/fulldisclosure/2020/Nov/22
http://seclists.org/fulldisclosure/2020/Nov/20