This issue was addressed with improved state management of S/MIME encrypted emails. This issue is fixed in macOS Monterey 12.6.8. A S/MIME encrypted email may be inadvertently sent unencrypted.
https://support.apple.com/en-us/HT213844
https://blog.aegrel.ee/apple-mail-smime.html
Source: Mitre, NVD
Published: 2023-09-12
Updated: 2024-01-30
Base Score: 7.8
Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:N/A:N
Severity: High
Base Score: 7.5
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N