dbcve.org
macOSOperating system · Apple

CVE-2023-40440

HIGH · 7.5 CVSS v3.1 Published 2023-09-12
Fix available
A fix is available. Upgrade to 12.6.8 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A state management vulnerability in macOS Monterey's Mail application causes S/MIME encrypted emails to be inadvertently sent unencrypted. The issue stems from improper tracking of encryption state during email composition, leading to potential exposure of sensitive email content despite the user intending encryption.

MitigationApply macOS Monterey 12.6.8 or later security update to address the state management flaw. Organizations should verify S/MIME encryption is functioning correctly after patching and consider email gateway-level encryption enforcement as a compensating control.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
macOSOperating system
Affected:>= 12.0.0, < 12.6.8

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Verify macOS Monterey version
    Run `sw_vers -productVersion` in Terminal or check System Settings > About > macOS version
    Affected if Version starts with 12.0.0 through 12.6.7 (any build before 12.6.8)
  2. Confirm Mail application is in use
    Launch Mail.app and verify it is the default email client or used for composition
    Affected if Mail.app is actively used for sending emails
  3. Check S/MIME encryption configuration
    Open Mail > Settings > Accounts > select account > Account Information > check for S/MIME signing/encryption certificates configured under the Security tab
    Affected if S/MIME encryption is enabled and certificates are configured for outgoing mail
  4. Inspect Mail preferences for encryption state
    Examine ~/Library/Containers/com.apple.mail/Data/Library/Preferences/com.apple.mail.plist for encryption-related keys, or check if 'Encrypt by Default' is set in Mail > Settings > Composing
    Affected if Default encryption is enabled but may not be respected during composition due to the state management flaw

User is affected if running macOS 12.0.0 through 12.6.7 with S/MIME encryption configured in Mail.app, as the vulnerability can cause encrypted emails to be sent unencrypted without obvious user notification.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 12.6.8 or later
Fixed in 12.6.8
Interim mitigation

Apply macOS Monterey 12.6.8 or later security update to address the state management flaw. Organizations should verify S/MIME encryption is functioning correctly after patching and consider email gateway-level encryption enforcement as a compensating control.

Recommended fix High confidence

macOS Monterey 12.6.8

  1. Back up your Mac using Time Machine or another backup solution before proceeding
  2. Open System Preferences (or System Settings on macOS Ventura and later)
  3. Click on "Software Update" to check for available updates
  4. If macOS Monterey 12.6.8 is available, click "Update Now" to download and install the security update
  5. Alternatively, download macOS Monterey 12.6.8 from the Apple Support website and run the installer
  6. After installation, restart your Mac when prompted to complete the update
  7. Verify the update was successful by checking System Settings > General > About > macOS version
Caveat Point release updates typically have minimal breaking changes; however, always review release notes before updating production systems

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in macOS Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA1.0 h
10.0 hours of engineering $1,750
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-40440 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data