An out-of-bounds write issue was addressed with improved bounds checking. This issue is fixed in tvOS 14.3, macOS Big Sur 11.1, Security Update 2020-001 Catalina, Security Update 2020-007 Mojave, iOS 14.3 and iPadOS 14.3, iCloud for Windows 12.0, watchOS 7.2. Processing a maliciously crafted image may lead to arbitrary code execution.
https://support.apple.com/en-us/HT212145
https://support.apple.com/en-us/HT212011
https://support.apple.com/en-us/HT212009