CVE-2017-13871
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 · uneditedAn issue was discovered in certain Apple products. macOS before 10.13.2 is affected. The issue involves the "Mail" component. It allows remote attackers to read cleartext e-mail content (for which S/MIME encryption was intended) by leveraging the lack of installation of an S/MIME certificate by the recipient.
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 confidenceThis vulnerability in macOS Mail (before 10.13.2) allows remote attackers to read cleartext email content that was intended to be protected by S/MIME encryption. The flaw occurs when the email recipient has not installed an S/MIME certificate - the Mail application fails to properly handle the encrypted message and renders it in cleartext, bypassing the sender's encryption intent.
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< 10.13.2CVSS 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:3.0/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 checksWork through these to decide whether this CVE applies to you.
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Verify macOS versionRun 'sw_vers -productVersion' in Terminal or check Apple menu > About This MacAffected if Version is below 10.13.2 (e.g., 10.13.1, 10.13.0, 10.12.x, etc.)
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Confirm S/MIME certificate presenceOpen Keychain Access and search for certificates with 'S/MIME' or look in Login > My Certificates. Alternatively, in Mail go to Preferences > Accounts > select account > Advanced and check for S/MIME settingsAffected if No S/MIME certificate is installed for the mail account, or the certificate is expired/missing
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Test encrypted email renderingSend yourself an S/MIME encrypted email from another account, or inspect a received encrypted email. Check if it displays as cleartext without requiring any decryption actionAffected if Encrypted emails render in cleartext without prompting for a certificate or decryption PIN, indicating the bypass is occurring
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Check Mail preference settingsIn Mail > Preferences > Security, examine whether 'Decrypt messages using S/MIME' is enabled or if there are any certificate-related warningsAffected if Mail shows certificate warnings or indicates no valid S/MIME certificate is configured for the recipient
You are affected if running macOS below 10.13.2 AND receiving S/MIME encrypted emails on a system without a valid S/MIME certificate installed, causing those encrypted messages to display in cleartext.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor data10.13.2
Update macOS to version 10.13.2 or later to patch the vulnerability. Additionally, ensure S/MIME certificates are properly installed and configured on recipient systems to prevent cleartext exposure of encrypted emails.
- Consultation2.0 h
- Implementation3.0 h
- Testing2.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2017-13871 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2017-13871 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- 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
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