UPDATE: A patch has been issued in iOS 13.4.5 beta, with an expected final release soon. No word on patches for earlier iOS versions.
Source: https://threatpost.com/apple-patches-two-ios-zero-days-abused-for-years/155042/
A zero-day exploit has been discovered in the iOS Mail app. The security hole has existed as far back as iOS 6 (September 2012), and extends to the current iOS (13.x).
As of today (4/22/2020) this has NOT been patched. It is recommended that you DISABLE iOS mail at this time.
We advise that you update as soon as an iOS patch is available.
Full details at https://blog.zecops.com/vulnerabilities/unassisted-ios-attacks-via-mobilemail-maild-in-the-wild/