What is CVE-2023-40440?

CVE-2023-40440 is a high-severity vulnerability in Apple macOS. CVSS score: 7.5/10. Published 2023-09-12.

How severe is CVE-2023-40440?

High severity. CVSS v3 base score is 7.5 out of 10.

Vulnerability in Apple macOS

CVE-2023-40440

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.

Published 2023-09-12 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.

EPSS exploit prediction

EPSS: 0.005 (43.9th percentile), scored 2026-10-03.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 43.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: +0.000

Affected products

Apple macOS — versions unspecified

References

support.apple.com/en-us/HT213844 (Release Notes, Vendor Advisory)
blog.aegrel.ee/apple-mail-smime.html

Frequently asked questions

What is CVE-2023-40440?: CVE-2023-40440 is a high-severity vulnerability in Apple macOS. CVSS score: 7.5/10. Published 2023-09-12.
How severe is CVE-2023-40440?: High severity. CVSS v3 base score is 7.5 out of 10.