Enterprise LinuxOperating system · Redhat
CVE-2018-12373
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 · unediteddDecrypted S/MIME parts hidden with CSS or the plaintext HTML tag can leak plaintext when included in a HTML reply/forward. This vulnerability affects Thunderbird < 52.9.
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 confidenceIn Thunderbird versions prior to 52.9, S/MIME encrypted email parts that are visually hidden using CSS display:none or plaintext HTML tags can be inadvertently included in plaintext form when a user replies to or forwards such messages as HTML. This causes encrypted content to leak in cleartext.
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
Enterprise LinuxOperating system
= 6.0= 7.0= 7.5= 7.6
Enterprise Linux DesktopOperating system
= 6.0= 7.0
Enterprise Linux ServerOperating system
= 6.0= 7.0
Enterprise Linux WorkstationOperating system
= 6.0= 7.0
Debian LinuxOperating system
= 8.0= 9.0
Ubuntu LinuxOperating system
= 14.04= 16.04= 17.10= 18.04< 52.9.0CVSS 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
- Required
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/PR:N/UI:R/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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Identify Thunderbird versionOpen Thunderbird and go to Help > About Thunderbird, or run 'thunderbird --version' from command lineAffected if Version is below 52.9.0
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Confirm S/MIME encryption usageCheck email account settings: Edit > Account Settings > End-to-End Encryption. Look for S/MIME certificates configured.Affected if S/MIME is enabled and configured for encrypted email
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Test for hidden content in encrypted emailsReceive an S/MIME encrypted email, inspect its HTML source (View > Message Source) to see if it contains CSS display:none blocks or hidden HTML elements that contain plaintext contentAffected if Encrypted emails contain visually hidden elements that would be included in replies/forwards as plaintext
User is affected if running Thunderbird version below 52.9.0, uses S/MIME encryption, and handles encrypted emails with CSS-hidden or HTML-hidden content that could leak in plaintext when replying or forwarding.
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 data52.9.0
Upgrade Thunderbird to version 52.9 or later. Until then, avoid replying to or forwarding S/MIME encrypted emails that contain hidden content using CSS or plaintext HTML tags.
Fix this in Enterprise Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation2.0 h
- Testing1.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,744.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2018-12373 — 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-2018-12373 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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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.
- 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