GAEN (aka Google/Apple Exposure Notifications) through 2021-04-27 on Android allows attackers to obtain sensitive information, such as a user's location history, in-person social graph, and (sometimes) COVID-19 infection status, because Rolling Proximity Identifiers and MAC addresses are written to the Android system log, and many Android devices have applications (preinstalled by the hardware manufacturer or network operator) that read system log data and send it to third parties. NOTE: a news outlet (The Markup) states that they received a vendor response indicating that fix deployment "began several weeks ago and will be complete in the coming days."

A privilege escalation vulnerability impacting the Google Exposure Notification Verification Server (versions prior to 0.23.1), allows an attacker who (1) has UserWrite permissions and (2) is using a carefully crafted request or malicious proxy, to create another user with higher privileges than their own. This occurs due to insufficient checks on the allowed set of permissions. The new user creation event would be captured in the Event Log.

An issue was discovered in the GAEN (aka Google/Apple Exposure Notifications) protocol through 2020-10-05, as used in COVID-19 applications on Android and iOS. The encrypted metadata block with a TX value lacks a checksum, allowing bitflipping to amplify a contamination attack. This can cause metadata deanonymization and risk-score inflation. NOTE: the vendor's position is "We do not believe that TX power authentication would be a useful defense against relay attacks.

An issue was discovered in the GAEN (aka Google/Apple Exposure Notifications) protocol through 2020-09-29, as used in COVID-19 applications on Android and iOS. It allows a user to be put in a position where he or she can be coerced into proving or disproving an exposure notification, because of the persistent state of a private framework.