Description
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.
References (4)
Core 4
Core References
Third Party Advisory x_refsource_misc
https://blog.google/inside-google/company-announcements/update-exposure-notifications
Exploit, Mailing List, Third Party Advisory x_refsource_misc
http://seclists.org/fulldisclosure/2020/Oct/12
Third Party Advisory x_refsource_misc
https://github.com/google/exposure-notifications-internals/blob/main/en-risks-and-mitigations-faq.md#additional-considerations
Exploit, Third Party Advisory, VDB Entry x_refsource_misc
http://packetstormsecurity.com/files/159496/GAEN-Protocol-Metadata-Deanonymization-Risk-Score-Inflation.html
Scores
CVSS v3
5.9
EPSS
0.0244
EPSS Percentile
82.1%
Attack Vector
NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
Details
CWE
CWE-294
Status
published
Products (1)
exposure_notifications_project/exposure_notifications
< 2020-10-05 (2 CPE variants)
Published
Oct 07, 2020
Tracked Since
Feb 18, 2026