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Fencer Vulns
medium 5.9

CVE-2020-24722 json

An issue was discovered in the GAEN (aka Google/Apple Exposure Notifications) protocol through 2020-10-05, as used in COVID-19 applications…

published 2020-10-07 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-17433

cvss
5.9
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.5%
EPSS 2.5% chance of exploitation in 30 days, percentile 84%
public exploits
0
none known

Summary

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.

Exploit prediction

2.46% chance of exploitation in the next 30 days, higher than 84% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • seclists.org http://seclists.org/fulldisclosure/2020/Oct/12 referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/159496/GAEN-Protocol-Metadata-Deanonymization-Risk-Score-Inflation.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N
NVD 2.0 2.6 AV:N/AC:H/Au:N/C:N/I:P/A:N

Classification

Weakness
  • CWE-294 Authentication Bypass by Capture-replay

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.