Ubuntu LinuxOperating system · Canonical
CVE-2020-12398
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 · uneditedIf Thunderbird is configured to use STARTTLS for an IMAP server, and the server sends a PREAUTH response, then Thunderbird will continue with an unencrypted connection, causing email data to be sent without protection. This vulnerability affects Thunderbird < 68.9.0.
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 confidenceWhen Thunderbird is configured to use STARTTLS for IMAP and the server sends a PREAUTH response, Thunderbird incorrectly continues with an unencrypted connection instead of properly establishing TLS encryption, causing email data to be transmitted 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
Ubuntu LinuxOperating system
= 16.04= 18.04= 19.10= 20.04< 68.9.0CVSS 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
- 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 checksWork through these to decide whether this CVE applies to you.
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Check if Thunderbird is installedOn Linux, run: dpkg -l | grep thunderbird or which thunderbird. On Windows, check Program Files for Thunderbird folder.Affected if Thunderbird is not installed or no IMAP accounts are configured, the vulnerability does not apply.
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Determine installed Thunderbird versionRun: thunderbird --version or check Help > About Thunderbird in the application.Affected if Version is 68.9.0 or higher, the vulnerability is patched. Versions below 68.9.0 are affected.
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Identify IMAP account configurationOpen Thunderbird, go to Account Settings, expand the IMAP account, and check Server Settings. Look for the Server hostname and Port number.Affected if IMAP is configured to use port 143 with STARTTLS (not port 993 with SSL/TLS), the vulnerable code path can be triggered.
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Verify STARTTLS is enabled for IMAPIn Account Settings > Server Settings, locate the 'Connection security' dropdown option.Affected if Connection security is set to STARTTLS (rather than SSL/TLS or None), the vulnerable code path is active when the server sends a PREAUTH response.
User is affected if Thunderbird version is below 68.9.0 AND an IMAP account is configured to use STARTTLS on port 143, allowing the server to trigger the PREAUTH flaw and transmit email 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 data68.9.0
Upgrade Thunderbird to version 68.9.0 or later to receive the security patch that properly handles PREAUTH responses during STARTTLS negotiation.
Fix this in Ubuntu Linux
Scoped from the published advisory
- Consultation1.0 h
- Implementation1.0 h
- Testing1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $1,200.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-12398 — 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-2020-12398 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
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