With Beta 4.1, Android 12 is almost ready to launch, but until then Android 11 with the September security patch is now available for the Pixel 3, Pixel 3a, Pixel 4, Pixel 4a, Pixel 4a (5G), Pixel 5, and Pixel 5a.
There are 17 issues resolved in the September security patch dated 2021-09-01 and 23 for 2021-09-05. Vulnerabilities range from moderate to critical, with the most severe relating to the media framework and a remote attacker possibly executing arbitrary code through a crafted file.
In the last Android Security & Privacy Year in Review, Google notes that “no critical security vulnerabilities affecting the Android platform were publicly disclosed without a security update or mitigation available for Android devices.” Additionally, there was an 84% year-over-year jump in security patches during Q4 2018 compared to the prior year.
The Pixel 5a gets a cumulative update from the June security patch. There are separate builds for the US and Japan (Softbank, KDDI, Rakuten).